Marco Rubio's Stoked For Josh Rosen, Best Dolphins QB Since Dan Marino!

Marco Rubio is PUMPED Miami traded for Josh Rosen ... telling TMZ Sports the former Arizona Cardinal is now the best QB the Dolphins have had in TWO DECADES!!!

"He's the most talented passer we've had on the roster since Marino," the Florida Senator says.

Miami unloaded its second-round pick in last week's NFL draft to get JR from Arizona ... and Rubio is ALL FOR IT -- telling us it's basically a win-win for his favorite football team.

And why? Rubio says because Rosen came with such a team-friendly contract ... there's no risk at all for his squad.

"If it works out, great!" Rubio says ... "If it doesn't, we'll have to draft someone next year."

It's been a rough start for Josh's NFL career ... dude completed just 55 percent of his passes and threw just 11 touchdowns to 14 interceptions last season.