Louisiana-Monroe (19-9, 13-4) remains tied with Georgia Southern for first place in the Sun Belt Conference.
Roberson finished just one shy of his career-high, and shot 6 of 9 from the free throw line. Deng and Tylor Ongwae each finished with 14 points, and Deng added 13 boards.
The Jaguars (9-20, 7-11) trailed by 11 points after the start of the second half, but six-straight from Ken Williams cut the difference to three with 13:48 to play. South Alabama then went the next 3:44 without a point, and Louisiana-Monroe took off from there.
Williams scored 21 points, hitting four 3-pointers, to lead the Jaguars. South Alabama was out-boarded 41-29, and committed 14 turnovers.