Trying to redirect certain directories on system to external card.

[sunwind]

I am using FSTAB to do this with:

proc            /proc           proc    defaults          0       0
PARTUUID=97a6378b-01  /boot           vfat    defaults          0       2
PARTUUID=97a6378b-02  /               ext4    defaults,noatime  0       1

# Mount SD by UUID to /home/pi/SDMount
#UUID=5271-5048 /media/usb0 vfat auto,nofail,noatime,users,rw,uid=pi,gid=pi 0 0 - (If I use this method, the USB drive is never mounted even though it can be seen via hardware)
/dev/disk/by-uuid/5271-5048 /media/usb0 vfat auto,nofail,noatime,users,rw,uid=pi,gid=pi
# Bind Subdirs to RetroPie dirs
/media/usb0/BIOS /home/pi/RetroPie/BIOS none auto,nofail,noatime,users,rw,uid=pi,gid=pi,bind 0 0
/media/usb0/roms /home/pi/RetroPie/roms none auto,nofail,noatime,users,rw,uid=pi,gid=pi,bind 0 0

/media/usb0/rpi-config/opt /opt/retropie none auto,nofail,noatime,users,rw,uid=pi,gid=pi,bind 0 0

/media/usb0/rpi-config/etc /etc/emulationstation none auto,nofail,noatime,users,rw,uid=pi,gid=pi,bind 0 0

# Mirror Scripts to USB-SD
/media/usb0/scripts /home/pi/scripts none auto,nofail,noatime,users,rw,uid=pi,gid=pi,bind 0 0

# Mirror Savegame/states to USB-SD
/media/usb0/savestates /home/pi/RetroPie/SaveStates none auto,nofail,noatime,users,rw,uid=pi,gid=pi,bind 0 0
/media/usb0/SaveGames /home/pi/RetroPie/savefiles none auto,nofail,noatime,users,rw,uid=pi,gid=pi,bind 0 0

# a swapfile is not a swap partition, no line here
#   use  dphys-swapfile swap[on|off]  for that

The device can see the SD card contents in the appropriate places:

But there are no systems or anything in the main menu screen area. any ideas?

[mitu]

Looking at the last screenshot, your ROM folder are named differently than what EmulationStation is configured to look after (snes, saturn, megadrive, etc), so they're probably ignored.

From your mounting schema, I see you're using a FAT32 drive and you're trying to mount the whole /opt/retropie (!) on it, under the pi user. This is not correct and it's going to cause issues - you shouldn't do that. And probably /etc/emulationstation should be left also alone - if you want to edit it, just create your own customized es_systems.cfg in $HOME/.emulationstation/ and use it.