For fishynes :
I have all my .nes roms (unzipped) in: "/mnt/sd/roms/nes"
Forget the "mnt/sd" if you use a usb card reader, just put your .nes roms on your Sd card, in directories like this : /roms/nes
EDIT : for SquidgeSnes you should put your roms in the SquidgeSnes directory/roms.