[2] In his junior season, Roby averaged 12.5 points, 9.8 rebounds, 2.6 steals and 3.7 blocks per game, earning second-team all-state Class 3A honors.

Roby finished eighth in Illinois Mr. Basketball voting and was named second-team all-state by the Chicago Sun-Times.

[6][7][8] Roby entered his freshman season for Nebraska in 2016–17 with a pelvic stress reaction suffered in the offseason, delaying his college debut.

He also led his team in field goal percentage, shooting 57 percent, and compiled 63 blocks, the most by a Nebraska player since 2001.

[19] On January 24, 2020, Roby was traded to the Oklahoma City Thunder by the Mavericks in exchange for Justin Patton and cash considerations.

On December 29, 2020, Roby scored a season-high 19 points, alongside seven rebounds and two blocks, in a 107–118 loss to the Orlando Magic.

[21] On March 28, 2022, Roby scored a career-high 30 points, alongside eight rebounds, four assists and two steals, in a 134–131 win over the Portland Trail Blazers.