Rick Ross' tour bus was left in ruins Saturday ... after a burglar (or burglars) broke into the massive vehicle, plundered thousands of dollars worth of stuff, and practically destroyed it in the process.

Detroit law enforcement sources tell TMZ, Ross' camp filed a police report early Saturday morning, claiming the bandits made off with thousands of dollars worth of jewelry, clothes, and other personal property.

We're told no one was inside the tour bus when it was burglarized. Ross and his entourage were staying at a nearby hotel at the time.

So far, there are no suspects.