If your roms end in the a52 extension or zip you need to use the atari menu option then select cartridge management then insert cartridge then select the type of 5200 cart it is then select warm reboot. The only problem with this emu is getting the controls right its kind of a pain.
Well, that worked for Asteroids, now....but, again...NO FRIGGING START BUTTON!!
Dingux-7800 doesn't require this sort of a pain in the ass.
Well, it works for SOME games, got Berzerk to go fine, but same no start button problem...on the other hand, Centipede and Defender got the crash screen...but at least this time the title and year showed up under the Atari Logo...but still got the crash screen on those two games.