UNC's Roy Williams LOCKER ROOM TURN UP ... After Beating Gonzaga

Roy Williams got LIT in the locker room!!!

The North Carolina coach fueled the crazy post-game celebration right after the Tar Heels beat the Zags in the NCAA Championship game ... screaming, yelling, showering people with non-alcoholic beverages.

The legendary coach even gave his guys an impromptu math test about how the tournament went from 64 teams down to 1 ... see, academics matter!