12:20 PM PT -- LVMPD says Roger has been located by family members ... he's safe and is currently being monitored. We're told cops are trying to figure out where exactly he went.
As for Floyd ... sources close to Mayweather tell us the boxer was in Toronto on vacation with his kids ... and is on his way back to Vegas to check on his Uncle.
Floyd Mayweather's Uncle, Roger Mayweather -- one of the most famous boxing trainers in the world -- has gone missing ... and family members are concerned, saying he needs his medication as soon as possible.
Roger was also a pretty good boxer ... and battled with some pretty big starts, including Julio César Chávez and Ray "Boom Boom" Mancini.
The LVMPD has issued an official missing persons alert ... saying Roger was last seen Saturday afternoon near the Mayweather Boxing Club in Las Vegas.
He's 5'7" and 160 lbs. He was last seen wearing a white shirt, blue sweatpants, and white shoes.
Cops also believe Roger is suffering from health issues, and needs medication.
Cops say anybody with information should go to police ASAP.