Emulators and Roms

Emulators

You can find a list of emulators here https://emulation.gametechwiki.com/index.php/Main_Page

Roms

There are a variety of places you can find ROMS. Personally the r/roms megathread is the place to go. Anything that is "no-intro" or "redump" has been verified by the community to be a good dump.