But Palhares and Camozzi have both been sidelined with unspecified injuries. So UFC.com announced on Wednesday that Okami and Roberts will tangle at Denver's Pepsi Center instead.
For Okami, ranked No. 9 in the most recent MMAFighting.com middleweight rankings, Roberts represents his third UFC 150 foe. The Japanese star was first slated to fight Luiz Cane, then when Cane pulled out with an injury, Palhares took his place.
Roberts (12-2), a Jackson's MMA fighter, now has a big opportunity to step up in competition and make a name for himself. He won his UFC debut against Calo Magalhaes via unanimous decision on June 8, his sixth straight win and 10th in his past 11 fights.
Okami (26-7) is looking to shake off a two-fight losing streak. He was stopped by middleweight champion Anderson Silva last August and was TKOd in the third round against Tim Boetsch in February after dominating the first two rounds.