JAY Z VISITS MIGUEL COTTO TRAINING CAMP ... Before Huge Fight

Here's Jay Z checking on one of his biggest investments -- boxer Miguel Cotto -- making sure he's ready to rumble when he steps into the ring with Canelo Alvarez next month. 

Jay stopped by Wild Card Gym in Los Angeles -- where trainer Freddy Roach also trains Manny Pacquiao -- and watched as the Roc Nation Sports boxer prepped for his Nov. 21 title fight.

As our friends at BSO pointed out, it's a huge fight for Jay Z -- who reportedly inked Cotto to a $55 MILLION contract back in March. 

"If Cotto wins, it is on to bigger and better things (more money for Hov)," BSO says ... "If he loses, then back to the drawing board."

FYI -- Alvarez is currently the favorite ... but everyone likes an underdog, right? 

"Invest in the brand!"