Rolando Romero Says He'll Knock Tank Davis 'The F*** Out'

"Tank's gonna knocked the f*** out. And, whoever believes otherwise can go f*** themselves."

That's 26-year-old, undefeated rising boxing star Rolando Romero -- aka Rolly -- declaring that he will not only beat Gervonta Davis when they fight December 5 in Los Angeles, but Tank will get flatlined within 3 minutes!!!

It's an incredibly bold prediction ... especially considering most experts have picked Davis to beat the very talented Romero.

But, Rolly -- who we spoke with leaving Wilder-Fury 3 -- is adamant he isn't just running his mouth ... he believes he's got a size and power advantage.

"The best thing about Tank is that he's a puncher, and I'm a bigger puncher and bigger person. What the f*** does he have?" Rolly tells us.

"I punch way harder than him. Ask anyone that knows us both. They'll tell you straight up."

Of course, Tank is known as one of the hardest punchers, pound-for-pound, in the entire sport. All but 1 of his 25 wins are by knockout ... and the uppercut he dropped Leo Santa Cruz with is one of the most devastating punches of all time.

But, Rolly's power definitely isn't anything to scoff at ... all but 2 of his 14 wins are also by KO.

So, Romero's prediction?!?

"I'm gonna knock him the f*** out."

When?!?