It's just a matter of time before Ronda Rousey officially signs with Vince McMahon -- so says WWE legend, Jim Ross , who says it's a "match made in heaven."

"Oh, she's gonna be a big star," the WWE Hall of Famer told us at LAX ... "It's inevitable. I see her in a WrestleMania someday."

Rousey's been a huge pro wrestling fan for years -- and there have been rumors that she could follow in the footsteps of guys like Ken Shamrock and make the transition from the UFC to WWE.

Ross thinks that's 100% the right move. 

"It's too great an opportunity for her to pass up and WWE to pass up ... it's a match made in heaven."