wait a sec...sice when is running a rom and emulating a rom different?
Running a ROM means the hardware "understands" the code natively, and interprets commands, graphics, sounds, etc. directly. A machine emulating another console has to have the virtual console running (so that the code "thinks" it's running on the appropriate console), and translate and adapt every bit of code (because of differences in processor architecture), and convert every bit of graphics, into something that machine "understands", on the fly, and then run it.
A GBA
runs GBA ROMs; a PC with VisualBoy Advance
emulates the GBA to run ROMs, because the PC has x86 architecture and the GBA has ARM7.
To successfully emulate a processor you have to have a much faster machine, because it has to translate and adapt in real time, as well as "translating" and adapting player feedback, and actually run the code, in real time. That means up to hundreds of operations for every line of code in the original ROM.
And the DS is too slow to emulate, and trying to make it actually
interpret GBA code
directly would be way too much hassle.
Get a Slot2 flashcard, people