Is it Legal to use old Rock and Roll Songs on your Website selling Stereo equipment?

You must have permission written or otherwise to replay or broadcast a song whose original or current owner is unaware of the song being played, especially when you will use the song to market, advertise, or in the sale of any product. Yes, it is illegal. You won't go to jail. Unless you are owned by proctor & gamble or sony, I'll almost guarantee that you won't even be a blip on the radar screen and your sales so minimal that no one will even care or notice you. Do it, even if they do find out and care about it, they will send you a cease and desist court order from a judge telling you to take it down or stop using their song. Good luck.

Alternatively

You could take any song that has been distributed on records (copyright protected or not), record your own performance of the song, notify the copyright office and pay the compulsory license fee to digicast your own sound recording of the underlying copyrighted work.