Russell sank 2 of 3 from beyond the arc and all six from the foul line, while Odunsi finished 10 of 14 from the line.
Houston Baptist (8-8, 3-3 Southland) led by 13 at the break but had to fend off a second-half surge by Lamar, which pulled to within 71-70 after a pair of free throws from Tyran de Lattibeaudiere with 2:56 to go. Lamar again closed within one on a layup from Donovan Ross that made it 73-72 with 35 seconds left. Odunsi padded Houston Baptist's advantage from the free-throw line each time.
Anthony Holliday led Lamar (10-9, 4-3) with a career-high 30 points, and de Lattibeaudiere finished with 17 points.