Riller, 24, is 6-foot-2 and spent last season on a two-way deal with the Hornets. The 56th overall pick in 2020, he divided his time between the Hornets and Greensboro Swarm of the G League.
Riller appeared in seven games with the Hornets, averaging 2.6 points as a rookie after going undrafted out of Charleston.
Players on two-way contracts can appear in up to 50 games in the NBA. Undrafted rookie small forward Aaron Henry holds the 76ers’ other two-way spot.