"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 .