you can only use Roms which are .3ds format files if you have a flashcart, if you have a Custom Firmware you need to install the games in your 3ds sd card using a .cia file of the game and an application to install it like fbi. in both cases the game runs natively.Oh, ok...so the back ups are not roms? Typically, like for mame, roms are emulation of the original game.