Jeremy Roenick Can Help Bieber's Hockey Game

NHL legend Jeremy Roenick says he wants to personally mentor Justin Bieber on the ice -- telling TMZ Sports he GUARANTEES he can take JB's skills to the next level.

Roenick says he saw the new hockey footage Bieber posted online this week -- and was genuinely impressed ... but says the guy has serious room to grow.

"He's pretty tough up top, I don't know about the calves and the thighs though ... it's a little weak."

So, what's the plan?

Jeremy says he'll put together a REAL comprehensive hockey-based workout plan for Bieber -- noting, "I will make you a WAY better hockey player."