Find out what kinds of RPG music you like, why you like it, and go from there. There are so many different kinds of RPGs out there, and they need music to match, so you've got options. The other main thing to consider is keeping your music unique from what is already on the NGAP.
Mosaab
If you're going to make something for an RPG, you should make one for the battle scenes first. The fight music should all be something heavy and angry, like real music to fight to. It should be really fast as well. Not too many rpgs have good battle music.
kelwynshade
The battle theme will be something that'll take some time. The hardest song to write for any RPG would have to be the battle theme.
Good enough to make you wanna kill stuff, but not so annoying that once you hear it 4 or 5 times you'll be pressing the mute button
*cough*Blue Dragon Boss Battle theme*cough*