I've been trying to download emulators for Sega and Original Nintendo....?

The emulators I've found (dega and Rocknes - both from freeroms.com) don't seem to run the roms from the same site. Now Dega is looking for sms files, while the games are downloading as zip and extracting as smd files. RockNes on the other hand tries to play any file. The readme file says it has a zip reader, so i tried that. "Unsupported mapper." So I extracted the games which changed them to an nes file, and still "unsupported mapper". Maybe it's just the few games I've tried.. I tried about 3 a piece... but Maybe I'm doing something wrong?

I am trying to download a torrent for the Sega games, so the problem maybe fixed shortly... The Nintendo though... anyway, any thoughts?