If you want to run the Atari 5200 ROMs on this site you have a few emulator choices. There are probably more, but these
are the best of the best I could find:
Virtual
Super System(VSS) is a great emulator by Dan Boris. It now supports sound
and will run a couple of the hard-to-run games like Bounty Bob Strikes Back.
VSS is a DOS program.
Rainbow is
a 5200 emulator that will run on both Windows '95 and Macintosh. It is also
my personal choice - I use it to create the screenshots on this page.
The BIOS ROM is the ROM listed for the Atari 5200 Instruction Manual.
Atari 5200 Archive