yes and no! because some rom are too old! company who own it don't renew the copyright so it have expired! those rom consider legal! but some new rom like pokemon is illegal!
Actually some roms are not copyrighted, Home brewed and the like, which would not be considered warez. But most roms are copyrighted and distributed them would not be allowed and I'm pretty sure all copyrights last for life + 50 years or so. So no rom is going to have an expired copy right. Just some companies don't exist any more so people can get away with distributing their stuff aka abandonware.
In general, roms are warez. Copyright law lasts a lot longer than most people think.... I pretty much agree with everything superdav2 said.
Not sure about bidvertiser but considering adbrite is used on demonoid.com, I don;t think they consider it an issue. Amazes me how little folks understand about copyright: "company who own it don't renew the copyright so it have expired" *sigh* Only with the drug companies and that's a patent.
adbrite accepts everything as most of the torrent/warez sites are using it, so you can give it a try. The payout probably will be 2-5% of what adsense normally pays though