I keep getting a 'disc read error' on my PlayStation 3.

There are three possible reasons you could be receiving this error.

1. If your disc is brand new, the issue may be with your disc. Please contact Mad Catz customer support depending on which version of Rock Band you have. Correct contact information for your game will be in your game manual.
2. Check your disc for scratches or debris. Cleaning your disc may be all that you need to do. If your disc is severely scratched or chipped, though, you may need to purchase a new disc.
3. The laser on your console may be dirty or need replacing, in which case you'll need to contact Sony Customer Support.

Sony Web Customer Support: http://us.playstation.com/support/