Cops to Derek Fisher: Slow Your Roll!!

Derek Fisher was speeding down the 405 Freeway this week ... but don't worry, he WASN'T on the way to a rematch with Matt Barnes.

Law enforcement sources tell us ... the ex-Lakers star was clocked doing 80ish in a 65 on Wednesday night. No big deal, just a ticket and he was on his way.

The good news -- we're told Fisher couldn't have been nicer during the stop and didn't even try to play the "Do you know who I am?" card.