You will need the DS bios files (one for the ARM7 and one for the ARM9).
It is legally questionable to link the bios so I am afraid you will have to hunt for this (30 seconds and the use of google were enough to draw it out). The files you want are called biosnds7.rom and biosnds9.rom. You might also want to try to dump your own:
http://hp.vector.co.jp/authors/VA018359/nds/ndsbios.html
You need a copy of the firmware as well, this is a bit harder to come by online so I dumped it myself. There are a few firmware dumpers available but I used the SRAM dumper at
http://www.natrium42.com/blog/?p=20 with my EZ2, I had to take it off in multiple passes and stick it back together with the copy /b command. For the record I use flashme but that made no difference.
You will also need to encrypt the secure area, while there are multiple ways to pull this off eNDcryptS (
link ) is probably the easiest right now. I stuck the all in the same directory as no$gba and fired up eNDcryptS, the roms got encrypted thus using these files commercial roms can be played.
Do not expect much though.