ok, lets break this down into the two questions:
1 – Can you run two emulators at once? Yes and no. You probably could set it up somehow, I have no idea how but I do believe that it is possible because just about anything is “possible”. So no, you can’t do this right now lol
2 – How to get MAME roms working – Someone else should step in and help you here or you should check out the wiki for this project. I haven’t actually touched on MAME yet but I will give it a go right now and come back to this thread later.