As a junior in 2013, Roberson earned first-team all-conference honors in the Pac-12 for the second time, and was also named the Pac-12 Defensive Player of the Year.

[3] At the end of his junior season, Roberson declared he was forgoing his remaining NCAA eligibility to enter the 2013 NBA draft.

[9] Earning the Thunder's starting shooting guard spot for the 2014–15 season, Roberson recorded his first career double-double (10 points, 12 rebounds) on December 18 against the Golden State Warriors,[10] and scored a then career-high 12 points on February 9 against the Denver Nuggets.

[12] He retained the starting shooting guard spot in 2015–16, and on December 23, he scored a then career-high 15 points in a 120–85 win over the Los Angeles Lakers.

[15] In Game 4 of the Western Conference Finals, Roberson scored a career-high 17 points and grabbed 12 rebounds, as the Thunder defeated the Golden State Warriors 118–94 to take a 3–1 lead in the series.

Roberson was moved to the starting small forward spot for the 2016–17 season due to the loss of Kevin Durant and the acquisition of Victor Oladipo.

[24] On October 4, 2018, Roberson was ruled out for an additional two months after undergoing a procedure following a setback during his rehab from left knee surgery.

[25] In late November, Roberson experienced discomfort after landing from a jump, and an MRI revealed that he had suffered a small avulsion fracture in his knee.

[26] On August 1, 2020, Roberson played his first NBA game in more than two years, logging five minutes in a 110–94 win over the Utah Jazz.