Richard Jefferson & Luke Walton -- Stacking Chips on Vegas Craps Tables

Richard Jefferson likely dropped some of his new Cleveland Cavaliers dough on a craps table in Las Vegas, where he was hanging with his ex-teammate Luke Walton -- and hauling in the chips.

Vegas sources tell TMZ Sports the former U of A Wildcats were doing some serious high rolling at Aria last weekend ... wagering anywhere between $600 and $1,000 on each roll. We're told Luke walked away with about $20k in winnings, and Richard did even better.

Talk about a great guys' weekend -- we got video of the duo boarding a Southwest flight for Vegas, and they told us the real reason for the trip ... their fantasy football draft.

Jefferson's got a good shot at his first NBA championship after signing with LeBron and the Cavs -- and, of course, Walton just won his 3rd title (as a Golden State asst. coach). But sounds like all the weekend smack talk was about their FF championship.