NBA superstar and fashion icon Russell Westbrook says there's one fashion risk he REFUSES to take -- the male romper.

The OKC Thunder star is known for pushing the envelope when it comes to style -- he's rocked everything from overalls to heavy metal chic ... even did an Urkel theme. 

But when we saw Brodie leaving Il Pastaio in Bev Hills on Thursday, Russ made it clear you'll NEVER see him rockin' the rompHim ... the new fashion craze UFC champ Stipe Miocic can't stop talking about

In other news, Westbrook is pumped about being a new dad -- and can't wait for his first Father's Day!