The legality of ROMs is questionable at best. Even if ROMs are legal given you own the original, you (creator of said website) would never be able to prove that you knew your visitors owned copies of the games. Also, providing download access to ROMs, which are copyrighted material, is distributing.
All said and done, what you want to do, probably won't hold up to the TOS, and is a questionable practice at best.