I just got an RPi2 and installed RetroPie through the setup script. All seems to be working fine, except for the USB ROM Service. I enabled it, but when I plug in my 16GB drive, nothing happens. No roms folder gets generated, all I get is a (according to Windows) USB storage device with problems. These problems seem to be nonexistent, though.
The USB drive mounts to /media/usb0 just fine and it’s formatted in FAT32.