Douglas-Roberts, who played guard and forward for the Texas Legends, was averaging 18.7 points, 4.3 rebounds and 2.8 assists this season. He has played in 161 career games for the Nets, Bucks and Mavericks, averaging 7.5 points in NBA play.
Douglas-Roberts did not play in the Bobcats' 92-83 loss to the Orlando Magic on Wednesday night.
Southerland signed with Charlotte as a non-drafted free agent prior to the season. He saw action in only one regular-season game, playing three minutes.
Information from The Associated Press was used in this report.