@Mrtay101 One simple way would be to enter mc in the text console. This should start the file manager "Midnight Commander".
In it, you can navigate with your cursor keys, enter directories with Enter and going back to the former directory by entering the .. in the first line of the file list.
Using this, go to the directory RetroPie, then roms, then to the resp. system directory of your roms (e.g. arcade for arcade roms) and you should see your roms. Select the ones you don't need with your Insert key and delete them with F8. But be careful, deleted files can't be restored! (or not without extreme effort, if at all)
After making some space, leave mc with F10 and reboot your Pi in the console with the command sudo reboot.
You can find a more elaborate guide to mc here: https://www.thegeekstuff.com/2008/10/midnight-commander-mc-guide-powerful-text-based-file-manager-for-unix/
edit: Oh, and please change the title of this topic to a more descriptive one by editing your first post. There, you can change the title, too.
