Marie Osmond's Son, Michael Bryan, told roommates his girlfriend drugged him

Marie Osmond's late son, Michael Bryan, told his roommates that he believed a former girlfriend had drugged him to the point he blacked out three days before he jumped to his death ... sources tell TMZ.

We're told Michael's roommates told law enforcement they planned on going out with Michael three nights before he died ... but he told them he couldn't go because he had made plans.

Sources say Michael didn't come back to the apartment that night. When he finally returned home he told his roommates an ex-girlfriend had contacted him, saying she was in town. Michael told his roommates he had blacked out and eventually awakened, only to find himself laying in a street several blocks from his apartment. Michael told his roommates he believed the ex-girlfriend had drugged him.

The roommates told law enforcement Michael had been sick for the next two days ... up to the time he died.

We're told law enforcement contacted the ex-girlfriend, who says she wasn't even in town the night Michael claimed she drugged him.

The L.A. County Coroner's Office is awaiting toxicology reports to determine if drugs were in Michael's system when he died.