Where to (legally) acquire content to play on RetroPie

[themazingness]

Intellivision Lives! for Windows 95/Power Macintosh is a collection of 50 Intellivision roms on CD-ROM from 1998. The BIOS files are also on the disc. No need to install the program, just get exec.bin and grom.bin from the root folder and put those in your BIOS folder. Then go to INTYPC>INTYTECH>BINARIES to get the roms (they're organized in folders by game genre).

The collection isn't too hard to find at a good price. Don't confuse it with Intellivision Lives! for various consoles or Intellivision Greatest Hits for PC/Mac (not sure if the latter would have ROMS, but it does have less games).

Edit: The BIOS files are in uppercase. To work with RetroPie, rename them in lowercase.

[Auster]

On the topic of physical compilations of ROMs (sorry for the massive post in advance), the US release of Sonic Mega Collection Plus for PS2, GameCube and likely PC (only released as a physical edition) includes 17 ROMs, 11 for Mega Drive and 6 for Game Gear, and even a BIOS needed to run special modes in some Mega Drive games.

I learned the base for the process here: http://www.racketboy.com/forum/viewtopic.php?t=30647
But it still required a lot of figuring things out and far more time than I'm proud to admit.

I used the PS2 version, but it should work more or less the same in the other releases. (Will need to adapt the process with the tools available for your platform of choice.) Also, I'll check later if I can extract the BIOS from the Steam release of Sonic 3 & Knuckles as well.

And I couldn't figure out how to do the process on Linux, since apparently Unix systems handle RAM way different than Windows.

If you have this collection on the PS2 and want to extract the ROMs included, you'll need a few things: a bunch of PS2 save utility tools (listed during the process), a save with everything unlocked (Gamefaqs should have it), PCSX2, a hex editor and a computer that can handle PS2 emulation (doesn't matter if it's laggy).

First, how to get the full save into PCSX2:

Step 1:
If you got the save from a real PS2, skip this step.
If you got a PSV file (PS2 save generated in the PS3), get the program PSV Exporter:
https://www.ps2savetools.com/download/psv-exporter/
Then extract the tool, open it, click in "File", click in "Open PSV file", choose the file and, once loaded (should load fast), click on "File" again, click in "Extract all files" and choose the output directory.
It should output 3 files, one called "BASLUS-2091700" (no extension), one called "icon.sys" and one called "LIST.ICO".

Step 2:
Get the program PS2 Save Builder:
https://www.ps2savetools.com/download/ps2-save-builder/
Then open it, drag into it the 3 files you got either from an actual PS2 or the PS3's PSV file, type the name of the file without extension in the field to the right of "Root/ID" (such as BASLUS-2091700 for the US release), click in "file", click in "save as", type a name of your choice (doesn't matter what you type), select the file type as "AR MAX V3 (*.max)", choose the output folder and confirm.

Step 3:
Open PCSX2, open the Memory Card Manager and create a new memory card. Name whatever you want.
Also make sure it says "yes" in the "Formatted" column.
If it isn't formatted, while still inside the Memory Card Manager, select the the memory card, click in the "Insert" button and put in either the port 1 or 2 (doesn't matter which).
Then exit the Manager, click in "CDVD" option in PCSX2's main window and select "No Disc".
Then click in "System" in the main window and click in "Boot BIOS".
Then, in the emulation screen, wait for it to load, then click in "Browser".
Then open the memory card you inserted in the manager before (e.g. if you inserted it in Port 1, it'll be "Memory Card (PS2)/1").
It'll say the memory card is unformatted and it'll ask if you want to format it now. Choose "Yes".
Then close the emulator.

Step 4:
Download myMC:
http://www.csclub.uwaterloo.ca:11068/mymc/
Open it. If it complains about missing dll's or if it closes right after being opened, get both msvcp71.dll and msvcr71.dll and place them in the same folder as mymc.exe.
Then select the memory card you created in Step 3.
Then click on the memeory card symbol with a green arrow to its left.
Then open the .max file you created in Step 2. The program will automatically inject the save in the memory card and save the changes.
Close the program.

Now you have the full save in PCSX2.

Then the main part, extracting the ROMs.
First read the base process (first link). I'll be using the tool the creator of the original post suggested, HxD.

To make it easier for extracting the Genesis/Mega Drive ROMs, here's the expected lengths:

Sonic The Hedgehog: 80000
Sonic The Hedgehog 2: 100000
Sonic The Hedgehog 3: 200000
Sonic & Knuckles: 200000
Sonic 3D Blast: 400000
Sonic Spinball: 100000
Dr.Robotinik's Mean Bean Machine: 100000
Flicky: 20000
Ristar: 200000
Comix Zone: 200000
The Ooze (only Genesis game from this collection not released on Steam as well): 100000

To get Game Gear games, as well as Sonic & Knuckles UPMEM ROM (the lock on BIOS I mentioned in the beginning), the steps change a bit:

1 - Press Ctrl F, go to the first tab (text) and look for a text I'll be referring to as "text to look for" (it'll always be the first result)
2 - Once you find the first result, click click in the beggining of its line in the hex table (pressing the "Home" button also works)
3 - Hold the shift key and start pressing either the up arrow key or the page up key until the "lenght(h)" value in the botton of the window is the value I specify for that game (I'll be calling it "backwards value").
4 - Click in the beginning of the top line of your selection from the previous step (home key works again), then press Ctrl E and put the lenght in hexadecimal value as you'd do with the Genesis/Mega Drive games.
5 - Copy the hex table, open a new tab in HXD, then paste the table in this new tab, which you'll be saving as a .gg file.

Needed information:

BIOS (name it sk2chip.bin instead of a .gg file):
Text to look for (yes, this text sample is right): ÀÿØ!üs2mdÿü
Backwards value: 70
Lenght: 40000

Sonic The Hedgehog:
Text to look for: game gear
Backwards value: FFC0
Lenght: 40000

Sonic Labyrinth:
Text to look for: TMR SEGA
Backwards value: 7FF0
Lenght: 80000

Sonic Drift:
Text to look for: DRIFT (C) SEGA
Backwards value: 990
Lenght: 80000

Sonic Chaos:
Text to look for: GG SONIC¥CHAOS
Backwards value: C0
Lenght: 80000

Sonic Blast:
Text to look for: GG SONIC 96
Backwards value: C0
Lenght: 100000

Dr.Robotinik's Mean Bean Machine:
Text to look for: TMR SEGA
Backwards value: 7FF0
Lenght: 40000

[Auster]

Something I forgot about the BIOS:
If you plan to use it, Sonic & Knuckles' ROM needs to go with it in the emulator's BIOS folder.
And at least Genesis Plus GX on Retroarch expects the two files to be named properly.
The lock on BIOS should be named sk2chip.bin, and Sonic & Knuckles' ROM should be named sk.bin, and their sizes should be 256 KB and 2048 KB, respectively.

################################################################################

And I couldn't find sk2chip.bin's code in Sonic 3 & Knuckles' ROM from Steam, but I found something interesting:

If you paste Sonic & Knuckles' hex table to a new file, then you paste another game's hex table in this new file immediately after, you get ROMs that automatically load in special modes without the BIOS files placed in the emulator's BIOS folder.

The possible combinations I know of:

Sonic & Knuckles + Sonic 3 = Sonic 3 & Knuckles
Sonic & Knuckles + Sonic 2 + sk2chip.bin (add in this order) = Knuckles in Sonic 2
Sonic & Knuckles + Sonic 1 = Blue Sphere (and you can choose the map's random generation seed freely)
Sonic & Knuckles + any other game = Blue Sphere (with static random generation seeds that change from game to game)

################################################################################

Lastly, a question:

Did anyone manage to extract Sonic Adventure DX's ROMs from the Steam release?
It's listed in romextract's scripts, but I can't extract it (gives some error about prxstool and temp folders, even if I build the tool and place in the romextract's tools folder).
I also can't extract it with either WinRAR, 7-Zip or Linux's program Nautilus.

[Auster]

@auster said in Where to (legally) acquire content to play on RetroPie:

EDIT: The Uninvited for Macintosh might have some issues? It crashes for me after a certain point. The Apple IIgs works fine after the same point.

Little update:
It seems the emulator I was using to test (Basilisk II) is borked. It would freeze until I killed its process whenever a game (not just The Uninvited) would play sounds.
I tested another emulator (Mini vMac) and all 4 MacVenture games appeared to run fine.

[Auster]

Studio Vetea distributes some ROMs on Itchio.

The ones where I don't mention languages are available only in English.

The ones available so far:

Papi Commando Free Version (demo): https://vetea.itch.io/papi-commando-megadrive-version
Platform: Sega Genesis/Mega Drive
The downloadable file is the ROM. No need to rename or change its extension.

Papi Commando Remix (updated version of the game above): https://vetea.itch.io/papi-commando-remix-megadrive
Platform: Sega Genesis/Mega Drive
The downloadable file is the ROM. No need to rename or change its extension.

Papi Commando Remix DELUXE (appears to be the full version): https://vetea.itch.io/papi-commando-remix-deluxe
Platform: Sega Genesis/Mega Drive
Comes with 2 ROMs. The one with "V1" in the end of the name is the most recent update. Neither needs to be renamed or have their extensions changed.

Bomb on Basic City (full game): https://vetea.itch.io/bomb-on-basic-city
Platform: Sega Genesis/Mega Drive
The downloadable file is the ROM. No need to rename or change its extension. Both English and French language options are available in the ROM file. Also, the demo appears to no longer be available.

Bomb on Basic City Special Edition: https://vetea.itch.io/bomb-on-basic-city-special-edition
Platform: Sega Genesis/Mega Drive
The downloadable file is the ROM. No need to rename or change its extension. The ROM also includes a demo for Papi Commando Tennis, which you can open from the start screen. Both games included in the ROM have both English and French language options available.

Rol'An'Go (demo): https://vetea.itch.io/rolango-megadrive-edition-demo
Platform: Sega Genesis/Mega Drive
The downloadable file is the ROM. No need to rename or change its extension. Only available in French.

Papi Commando Reload (Tectoy's demo): https://vetea.itch.io/papi-commando-reload-free-demo-tectoy
Platform: Sega Genesis/Mega Drive
The downloadable file is the ROM. No need to rename or change its extension.

Papi Commando Tennis (demo): https://vetea.itch.io/papi-commando-tennis-bex-demo
Platform: Sega Genesis/Mega Drive
The downloadable file is the ROM. No need to rename or change its extension. Both English and French language options are available in the ROM file.

La Citadelle du Chaos: https://vetea.itch.io/la-citadelle-du-chaos-megadrive
Platform: Sega Genesis/Mega Drive
The downloadable file is the ROM. No need to rename or change its extension. Only available in French.

Papi Commando (demo): https://vetea.itch.io/papi-commando-official-demo-sega-master-system
Platform: Sega Master System
The downloadable file is the ROM. No need to rename or change its extension.

Papi Commando - Second Blood! (demo): https://vetea.itch.io/papi-commando-second-blood-megadrive
Platform: Sega Genesis/Mega Drive
The downloadable file is the ROM. No need to rename or change its extension.

PapiRium (demo): https://vetea.itch.io/papirium-official-demo
Platform: Sega Genesis/Mega Drive
The downloadable file is the ROM. No need to rename or change its extension.

[Auster]

Now available on Itch.io as well (still a demo):
https://morphcatgames.itch.io/sbpdemo

@cederick said in Where to (legally) acquire content to play on RetroPie:

Super Bat Puncher (There never was a full version)

[Auster]

(One week jam) GB Harvest by voxel: https://voxel.itch.io/one-week-jam-gb-harvest
Platform: GameBoy
The ROM is the file "harvest.gb"

SlipSpeed by voxel, tijn (both full release and shareware/demo): https://voxel.itch.io/slipspeed
Platforms: MS-DOS (DOSBox) & Windows 95
The MS-DOS version of both full release and demo is identified as such.

(Game Boy) Dashy no Witch by voxel: https://voxel.itch.io/dashy-no-witch
Platform: GameBoy
Has 2 ROMs, one incomplete (identified as such in the downloads page) and one complete (has 2019 in the name)

The Curse of Illmoore Bay, Sega Genesis ROM by Second Dimension R&T, LLC: https://seconddimensionllc.itch.io/the-curse-of-illmoore-bay
Platform: Sega Genesis/Mega Drive
I don't own the game so I can't check the files, but its name and where I found it indicate it is a Genesis ROM indeed.

Handy Harvy, Sega Genesis by Second Dimension R&T, LLC: https://seconddimensionllc.itch.io/handy-harvy-sega-genesis
Platform: Sega Genesis/Mega Drive
Same situation as above.

The following games are all NES games:

HACK*MATCH for the NES by Zachtronics: https://zachtronics.itch.io/hackmatch-for-the-nes
Don't own the game yet so I can't check the files, but the description mentions both NTSC and PAL ROMs.

Project Chocoblip Demo by Trirosmos: https://trirosmos.itch.io/project-chocoblip-demo
The ROM is the file named "Chocoblip_Post-Compo_v1.1.nes"

Altercation by The Doc: https://scottthephd.itch.io/altercation
The ROM is the file "altercation-0.1.nes"

Blockage by The Doc: https://scottthephd.itch.io/blockage
The ROM is the file "blockage-0.3.4.nes"

Blobert by MysticalWheelbarrow: https://mysticalwheelbarrow.itch.io/blobert
The ROM is the file "blobert.nes"

Hyperbeatz by MysticalWheelbarrow: https://mysticalwheelbarrow.itch.io/hyperbeatz
The ROM is the file "hyperbeatz_v1.2.nes"

No Good Choice (NESDev '20-21 Competition) by Yaroslav Veremenko: https://yaros.itch.io/no-good-choice-nesdevcompo
The ROM is the file "nogoodchoice-nesdevcompo2020.nes"

Trouble at 2a03 - NES rom by team_disposable: https://team-disposable.itch.io/trouble-in-2a03
The ROM is the file "trouble_in_2a03-nesdev-submission-build.nes"

Arlington Apple in an Interplanetary Pickle - NES Rom by team_disposable: https://team-disposable.itch.io/a-small-world
Has 2 ROMs, "ludum_dare.rc-7a.nes" and "ludum_dare.post-ld4.nes". The latter (post-ld4) is the most recent one.

You are insignificant - NES rom by team_disposable: https://team-disposable.itch.io/you-are-insignificant
The ROM is the file "YouAreInsignificant.nes"

Wolf Spirit - NES Game by valdirSalgueiro: https://valdirsalgueiro.itch.io/wolf-spirit
Has 2 ROMs, "WolfSpirit.nes" and "WolfSpirit1.1.nes".

NES platformer: https://valdirsalgueiro.itch.io/nes-platformer
The ROM is the file "platform.nes". Also, it's just a prototype of a platformer.

(Gamejam) ESCAPE FROM FLOODED CAVE by voxel: https://voxel.itch.io/escape-from-flooded-cave
The ROM is the file "flooded_cave.nes".

Carpet Shark (NES Homebrew) Fista Productions by Fista Productions: https://5kids2feed.itch.io/carpet-shark-nes-homebrew-fista-productions
The ROM is the file "CarpetShark.nes"

AO, NES Rom by Second Dimension R&T, LLC: https://seconddimensionllc.itch.io/ao-nes-rom
I don't own the game so I can't check the files, but its name and where I found it indicate it is a NES ROM indeed.

Eyra, the Crow Maiden NES ROM by Second Dimension R&T, LLC: https://seconddimensionllc.itch.io/eyra-the-crow-maiden-nes-rom
Same situation as above.

Family Picross NES Rom by Second Dimension R&T, LLC: https://seconddimensionllc.itch.io/family-picross-nes-rom
Same situation as above.

Get'em Gary by Second Dimension R&T, LLC: https://seconddimensionllc.itch.io/getem-gary
The ROM is the file "Get 'em Gary.nes".

[Auster]

@auster said in Where to (legally) acquire content to play on RetroPie:

@landyvlad said in Where to (legally) acquire content to play on RetroPie:

(...)
I'm wondering if Apple 2 and/or Atari 2600 games are legally available?

Nox Archaist comes with an Apple II ROM
(...)
Also, apparently, the games from the MacVenture series have Apple II ROMs
(...)

I got the information a bit wrong at that time:
Nox Archaist and the MacVenture series include Apple IIgs ROMs, and not Apple II ROMs.
Sorry for the confusion.

And talking about the Apple IIgs...

@themazingness said in Where to (legally) acquire content to play on RetroPie:

Lawless Legends is a cRPG for Apple II that is far into development and is open for testing: http://www.lawlesslegends.com/

Ancient Legends is a complete cRPG for Apple II in the same engine: https://8bitweapon.com/2016/07/21/our-rpg-ancient-legends-released

Both games come with an Apple IIgs version as well. The ROMs are the .2mg files "Ancient Legends - 800k version.2mg" and "game.2mg" (this last one is Lawless Legends)

Ancient Legends is available in their Github page (and I didn't need to repack it to run in the emulator I use): https://github.com/badvision/lawless-legends/blob/master/Example Content/Ancient Legends/Disk images/Ancient Legends - 800k version.2mg

Lawless Legends is available on the devs' Dropbox (linked in their site, http://www.lawlesslegends.com/).

And if you don't boot the Apple IIgs emulator straight into the games, their executables are the .SYSTEM files inside them.

[Auster]

Super Hunchback: https://store.steampowered.com/app/1539070/Super_Hunchback/
Platform: GameBoy
The ROM is the file "game" in the folder [Steam install folder]/Super Hunchback/res (add the extension .gb to it and, if you want, rename it as well).

##########################################################################################################

The MacVenture series (Apple IIgs and Macintosh 68K/Mac II), which include Déjà Vu 1 and 2, Shadowgate and The Uninvited, is available on a "build your own bundle" from Fanatical, an official Steam key seller:
https://www.fanatical.com/en/pick-and-mix/build-your-own-summer-bundle
You can pick just the MacVenture series for 1 USD.

Just to remind, the extraction methods for the MacVenture series:

With bash scripts (if you're on Windows, you may need a Linux Subsystem for Windows or another bash compatibility tool): https://gitlab.com/vaiski/romextract/

With a tool for managing and extracting compressed files, such as 7-Zip or Ubuntu's default zip manager (works with The Uninvited, even if the method says otherwise): https://github.com/blorente/MacVenture-Extract-Guide

[Auster]

More games, now paid but claimable for free until June 30th (but feel free to pay for them if you like):

A Western Ballad by R-Doman: https://r-doman.itch.io/a-western-ballad
Platform: GameBoy
The ROM is the file "game.gb" inside the downloadable zip file (feel free to rename it, but keep the .gb extension).

Take It Racing by R-Doman: https://r-doman.itch.io/take-it-racing
Platform: GameBoy
The ROM is the file "game.gb" inside the downloadable zip file (feel free to rename it, but keep the .gb extension).

Chaos Lab by R-Doman: https://r-doman.itch.io/chaos-lab
Platform: GameBoy
The ROM is the file "game.gb" inside the downloadable zip file (feel free to rename it, but keep the .gb extension).

Hack-R by R-Doman: https://r-doman.itch.io/hack-r
Platform: GameBoy
The ROM is the file "game.gb" inside the downloadable zip file (feel free to rename it, but keep the .gb extension).

The dev also has other 2 GameBoy games, but they can't be downloaded right now, just played in the browser.

And this game is a demo:
Take It Racing 2 by R-Doman: https://r-doman.itch.io/take-it-racing-2
Platform: GameBoy
The ROM is the file "game.gb" inside the downloadable zip file (feel free to rename it, but keep the .gb extension).

[Auster]

More NES games:

The Tower of Turmoil: https://cuttercross.itch.io/the-tower-of-turmoil
The ROM is the downloadable .nes file

Project DART: https://cuttercross.itch.io/project-dart
The ROM is the downloadable .nes file

The Prying Eye (apparently just a demo for now): https://cuttercross.itch.io/the-prying-eye
The ROM is the .NES file inside the downloadable .zip file

Project Blue: https://toggleswitch.itch.io/projectblue
I don't own the game yet, but according to the description, the game comes with both a Japanese and English ROMs.

Trophy: https://the6502collective.itch.io/trophy
The ROM is the downloadable .nes file

Machine Cave: https://aeromangus.itch.io/machine-cave
The ROMs are the downloadable .nes files (each has a different update)

Rollie: https://optovania.itch.io/rollie
The ROMs are the downloadable .nes files (one is PAL and the other is NTSC)

Fox Hunt NES Demo: https://tolerantx.itch.io/fox-hunt-nes-demo-byteoff-2020
The ROM is the .NES file inside the downloadable .zip file

Nightmare Castle: The Original Demo: https://tolerantx.itch.io/nightmare-castle-the-original-demo
The ROM is the downloadable .nes file

Ashen House: https://crazygrouptrio.itch.io/ashen-house
The ROM is the .NES file inside the downloadable .zip file

2600 AD (Byte-Off 2020) (demo): https://crazygrouptrio.itch.io/2600-ad
The ROM is the .NES file inside the downloadable .zip file

Game Gyaru EX: https://crazygrouptrio.itch.io/game-gyaru-ex
The ROM is the downloadable .nes file

Turtle Party: Preview Edition: https://turtlerescuenes.itch.io/turtle-party-preview-edition
The ROM is the .NES file inside the downloadable .zip file

Turtle Paint Demo: https://turtlerescuenes.itch.io/turtle-paint-byte-off-2020
The ROM is the .NES file inside the downloadable .zip file

Turtle Rescue: Unwrapped Holiday Edition 2019: https://turtlerescuenes.itch.io/turtle-rescue-unhatched-holiday-edition-2019
The ROM is the .NES file inside the downloadable .zip file

Heather The Beheader (so far only a demo): https://generalgruntin.itch.io/heather-the-beheader
The ROM is the .NES file inside the downloadable .zip file

Blazing Rangers / 炎のレンジャーマン (demo, at least currently): https://firstpressgames.itch.io/blazing-rangers
The ROMs are the downloadable .nes files (one is Japanese and the other is English)

Pixel Poops: Number Two (New Years Special Preview) (demo): https://techmastergames.itch.io/pixel-poops-number-two-new-years-special-preview
The ROM is the downloadable .nes file

Pixel Poops: Number Two: https://techmastergames.itch.io/pixel-poops-number-two-nes
The ROM is the downloadable .nes file

Gift: https://wendelscardua.itch.io/gift
The ROM is the downloadable .nes file. The game is only in Portuguese.

HappyNESs: https://wendelscardua.itch.io/happyness
The ROM is the downloadable .nes file

Farming mushrooms in LOWAS: https://wendelscardua.itch.io/farming-mushrooms-in-lowas
The ROM is the downloadable .nes file

Blob Land: https://wendelscardua.itch.io/blobland
The ROM is the downloadable .nes file

Roguelore: https://wendelscardua.itch.io/roguelore
The ROM is the downloadable .nes file. The game is only in Portuguese.

Ouroboros: https://wendelscardua.itch.io/ouroboros
The ROMs are the downloadable .nes files (not sure what's the difference between the two)

Tourtoise: https://wendelscardua.itch.io/tourtoise
The ROM is the downloadable .nes file. There's only 2 words in Portuguese in the game, and they have their English translation right next to them.

Bare Metal: https://wendelscardua.itch.io/bare-metal
The ROMs are the downloadable .nes files. One of the ROMs is in Portuguese (the one with "português" in the file's name) and the other is in English.

Retropia: https://wendelscardua.itch.io/retropia
The ROMs are the downloadable .nes files. One of the ROMs is in Portuguese (the one with "português" in the file's name) and the other is in English.

ConTroll: https://wendelscardua.itch.io/controll
The ROM is the downloadable .nes file

Raddio: https://wendelscardua.itch.io/raddio
The ROM is the downloadable .nes file

Planter: https://wendelscardua.itch.io/planter
The ROM is the downloadable .nes file

RGB: https://wendelscardua.itch.io/rgb
The ROM is the downloadable .nes file

NES Calculator (it's a tool, and it works): https://wendelscardua.itch.io/nes-calculator
The ROM is the downloadable .nes file

[Auster]

Devwill Too MD: https://amaweks.itch.io/devwill-too-md
Platform: Sega Genesis/Mega Drive
The ROMs are the downloadable .bin files. Comes with both a ROM in Brazilian Portuguese and and one in English. Also comes with a demo, which is only in English.

Virgil's Purgatory: https://amaweks.itch.io/virgil
Platform: GameBoy
I don't own the game yet, but apparently it comes with two ROMs in English (with one being a monochrome version) and one in Portuguese.

Arapuca: https://amaweks.itch.io/arapuca
Platform: Sega Genesis/Mega Drive
The ROMs are the .bin files. It's only in Portuguese.

Devwill Too ZX/MSX: https://amaweks.itch.io/devwill-too-zx
Platforms: ZX Spectrum & MSX
I don't own the game yet, but according to the description, it comes with a ROM for each of these platforms. (also, emulate the 128K version of ZX to have in-game music in that version)

FoxyLand (demo): https://pscd.itch.io/foxyland
Platform: Sega Genesis/Mega Drive
The ROM is the .bin file inside the downloadable .7z file.

Bio Evil (tech demo): https://pscd.itch.io/bio-evil
Platform: Sega Genesis/Mega Drive
The ROM is the downloadable .bin file.

Debtor (demo): https://pscd.itch.io/debtor-sega-mega-drive-genesis-demo
Platform: Sega Genesis/Mega Drive
The ROM is the .bin file inside the downloadable .7z file.

Alien Cat 2 (demo): https://pscd.itch.io/alien-cat-2
Platform: Sega Genesis/Mega Drive
The ROM is the .bin file inside the downloadable .7z file.

Reknum (demo): https://pscd.itch.io/reknum
Platform: Sega Genesis/Mega Drive
Comes with 2 7z files, each with a .bin ROM inside. Likely Reknum_Demo_002.7z has the second update.

[Auster]

CRNVRS (en, updated version): https://dakicorp.itch.io/crnvrs-en-2021
Platform: GameBoy
The ROM is the .gb file inside the downloadable .zip file.

[Auster]

Borbo's Quest: https://frogsoft.itch.io/borbo
Platform: GameBoy
The ROM is the downloadable .gb file. Feel free to change the ROM's name, but remember to keep the .gb extension.

[Auster]

The repository for Lawless Legends and Ancient Legends also includes some small prototypes/proof of concept demos from Lawless Legends made for the Commodore 64:

https://github.com/badvision/lawless-legends/tree/master/Platform/C64/demos

Tested all 3 files in VICE and they worked fine.

[Auster]

Cosmic Courier: Trapped in Limbo: https://bryanrollins.itch.io/cosmic-courier-trapped-in-limbo
Platform: GameBoy
The ROM is the downloadable .gb file.

Witch n' Wiz: https://mhughson.itch.io/witch-n-wiz
Platform: NES
The ROM is the downloadable .nes file.

FROM BELOW: https://mhughson.itch.io/from-below
Platform: ​NES & Nintendo VS. System (arcade)
The NES ROM is the file downloadable from the option "NES ROM [version number]". The Nintendo VS. Arcade System ROM are the files from the option "Vs. System ROMs [version number]", and may need compiling to run in MAME and the like.

Street Fighter II NE (fan game & demo): https://parisoft.itch.io/street-fighter-ii-ne-demo
Platform: NES
The ROM is the downloadable .nes file.

Berzerk: https://parisoft.itch.io/berzerk
Platform: NES
Has 2 ROMs, both in the .nes format. Also mind there are some reports of certain emulators having different compatibilities with the ROMs, so if one ROM doesn't work, try the other.

DUCKSTROMA: https://narwhal.itch.io/duckstroma
Platforms: ZX Spectrum (either 48K or 128K), MSX & NES
Each downloadable file is a ROM for a specific system (properly identified). Also, the NES version is an old prototype.

PTM: https://narwhal.itch.io/ptm
Platform: ZX Spectrum (either 48K or 128K)
The ROM is the .TAP file inside the downloadable .zip file.

OCTUKITTY: https://narwhal.itch.io/octukitty
Platform: ZX Spectrum (either 48K or 128K)
The ROM is the .tap file inside the downloadable .zip file.

BLIMPGEDDON: https://narwhal.itch.io/blimpgeddon
Platform: ZX Spectrum (either 48K or 128K)
The ROM is the .tap file inside the downloadable .zip file.

Cocoa 2: Twenty Four Hour Parsley People: https://minilop.itch.io/24hour
Platform: ZX Spectrum 128K
Has 3 versions of the demo (the free files), one in English, one in Portuguese and one in Spanish, and it has 3 versions of the full release (the paid files), each with one of the languages mentioned before. The ROMs are the .tap files inside the downloadable files.

Cocoa and the Time Machine: https://minilop.itch.io/cocoa-and-the-time-machine
Platforms: ZX Spectrum (either 48K or 128K) & MSX
Has 3 files for ZX Spectrum 48K, each with a language (Portuguese, English & Spanish), 3 files for the ZX Spectrum 128K (also each with a language from the ones mentioned before) and 1 file for the MSX (only in English)

[themazingness]

@auster Wow, you are the master at finding these itch.io ROMS. Thanks for all the work you are doing!

[Auster]

@themazingness Glad to be of help!

Btw, a tip: if you see a homebrew game on Itchio, check the dev's other works. Chances are the game you saw isn't the only one that can be emulated. Following these devs helps too, so that you get notified of homebrew/emulation-related stuff from them (just mind your feed can get kinda spammy if you follow too many devs; I know by experience "<.< ).

And sorry for not making a single post with all the games I find, but I'd find a single post with 200+ games a bit overwhelming if I was a passer-by. (plus, it would take a long time to check so many games, specially since some things about some games are not quite clear, like Cocoa 1 only having multiple languages in the ZX Spectrum version)

And here's some more games:

La Reliquia: https://roolandoo.itch.io/lareliquia
Platforms: ​ZX Spectrum & MSX
The ROMs are the .tap (ZX) and .dsk/.rom (MSX) files inside the downloadable .zip files. Both have 2 versions, one in Spanish and one in English. And both ZX ROMs have 2 variants, one for 48K models, and one for 128K models.

S.o.L.o.: https://roolandoo.itch.io/solo
Platform: ZX Spectrum 128K
Has 2 versions, one in English, and one in Spanish. The ROMs are the .tap files inside the downloadable .zip files.

Black & White: https://greenwebsevilla.itch.io/black-and-white
Platform: ZX Spectrum 128K
Has a demo and a full release in the same page. The demo is the downloadable .tap file in the demo part of the page. I don't own the full game yet, but it's likely the same as the demo.

Ninjakul 2: The Last Ninja: https://greenwebsevilla.itch.io/ninjakul-2-the-last-ninja
Platform: ZX Spectrum 128k
I don't own the game yet, but according to to the description, it does come with a ROM.

Ninjakul in the AUIC Temple: https://greenwebsevilla.itch.io/ninjakul-in-the-auic-temple
Platform: ZX Spectrum 128k
The ROM is the downloadable .tap file.

Vampire Slayer (demo): https://greenwebsevilla.itch.io/vampire-slayer
Platform: ZX Spectrum 128k
Has two versions, one in English and one in Spanish. The ROMs are the downloadable .tap files. Also the dev (s) plan to make a full version of it in the future.

Bat Boy: https://greenwebsevilla.itch.io/bat-boy
Platform: ZX Spectrum (48/128K)
I don't own the game yet, but according to to the description, it does come with a ROM.

Vampire Vengeance: https://endaraues.itch.io/vampire
Platform: ZX Spectrum
The ROM is the downloadable .tap file.

Pumpkin Poe: https://endaraues.itch.io/pumpkin-poe
Platform: ZX Spectrum
The ROM is the downloadable .tap file.

Droid Buster: https://endaraues.itch.io/droid-buster
Platform: ZX Spectrum
The ROM is the downloadable .tap file.

AtomiCat: https://endaraues.itch.io/atomicat
Platform: ZX Spectrum
The ROM is the downloadable .tap file.

Soul of the Beast: https://aeriform.itch.io/beast
Platform: Atari 2600
The ROM is the downloadable .bin file.

[Auster]

First, a question: AtariAge is legit, right? I see them being mentioned a few times here, and I found even some BIOS files while looking at their site.

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Nebs 'n Debs: https://dullahan-software.itch.io/nebs-n-debs
Platform: NES
I don't own the game so I can't check, but by the description, it likely comes with a ROM.

CRNVRS (Portuguese version): https://dakicorp.itch.io/crnvrs-microconto
Platform: GameBoy
The ROM is the .gb file inside the downloadable .zip file.

Upsad Down: https://fadest.itch.io/upsad-down
Platform: NES
The ROM is the downloadable .nes file.

Asteroids Chasers: https://fadest.itch.io/achaser-gb
Platform: GameBoy
The ROM is the downloadable .gb file.

A Bug's Trip Redux Demo: https://fadest.itch.io/a-bugs-trip-redux-demo
Platform: Atari Lynx
The ROM is the downloadable .lnx file.

A Bug's Lynx: https://fadest.itch.io/a-bugs-lynx
Platform: Atari Lynx
The ROM is the .lnx file inside the downloadable .zip file.

Asteroids Chasers: https://fadest.itch.io/achasers
Platform: Atari Lynx
The ROMs are the downloadable .lnx files. Likely "AChasers20200816.lnx" is the most recent update.

Raid on TriCity: https://fadest.itch.io/raid-on-tricity
Platform: Atari Lynx
The ROM is the .lnx file inside the downloadable .zip file.

Leaf and the forgotten temple (Ynxa version): https://fadest.itch.io/ynxa
Platform: Atari Lynx
The ROM is the .lnx file inside the downloadable .zip file.

Yastuna - The Alchemy of Cubes: https://fadest.itch.io/yastuna-the-alchemy-of-cubes
Platform: Atari Lynx
The ROM is the .lnx file inside the downloadable .zip file.

Yastuna 2 - the Space Incident: https://fadest.itch.io/yastuna-2-the-space-incident
Platform: Atari Lynx
The ROM is the .lnx file inside the downloadable .zip file.

Saving Santa Tree - LynxMas 2020: https://fadest.itch.io/lynxmas-2020
Platform: Atari Lynx
The ROM is the .lnx file inside the downloadable .zip file.

Cyberpunk Experiment 2037: https://fadest.itch.io/cyberpunk-2037
Platform: Atari Lynx
The ROMs are the downloadable .lnx files. They appear to be identified by update date, such as "c37-20200421.lnx" being from the update from April 21, 2020.

Doodle World (both demo & full release): https://natepeters.itch.io/doodle-world
Platform: NES
The demo is the .nes file inside the downloadable .zip file in the store page. And I don't own the full release yet, but according to the description, it comes with a ROM too.

+18 game below, contains explicity sexual intercourse; don't open if you're a minor.
Mating Season GB: https://peddverse.itch.io/mating-season-gb
Platform: GameBoy
Has multiple .gb ROMs inside. The most recent one is probably the one with the most recent updates as well. Also by the description and the last time Itchio says the game had an update, it appears to be mostly complete, but ultimately abandoned.

[Clyde]

@auster said in Where to (legally) acquire content to play on RetroPie:

+18 game below, contains explicity sexual intercourse; don't open if you're a minor.

You know that this remark will make every minor click on that link, don't you? 😉