ok - i am not sure but i think Joomla can do the work with the help of some extensions of it found at http;//extensions.joomla.org
Those are not roms, just flash games. And I think you can create it with any CMS that has a downloads module.
You can use any kind of download manager. The fact that they're ROMs doesn't make them 'special', they're just files! Grab a download / file manager and stick it into Joomla and be done with it.
DocMan or Remository should be fine if you use Joomla. My point, though, was that ROMs are not special: they're just files. Instead of asking for 'something for ROMs' ask for a CMS file / download manager: more people will be able to answer your question that way. Pretty much every CMS out there has a manager of this sort... like I say, ask for suggestions for that, rather than ROMs and you'll get a better, more informed, response.
Do you actually have all the roms? Let me know if you do and are willing to provide a download for your repository. I will pay. Secondly if you want to start up something together. Bla Bla Yaddy ya.. anyway PM me.