NRX has its rom definitions inside of itself, and you can't add more. But it does no CRC checks, it looks at the format of the file names, and also checks inside the roms. If that checks out, it will try to run it. Most NRX versions cannot do complex functions such as decryption or bank switching, so you need to find already-decrypted or hacked roms for most sets made after 1999. The rom names need to be (for example) something like this: pnya_p1.rom pnya_s1.rom pnya_m1.rom pnya_c1.rom pnya_c2.rom etc etc. Zip the roms into a zipfile, eg PoochiAndNyaa.zip NRX can use zipfiles of any name, so be creative.