Knowles grabbed 10 rebounds, Brandon Pye added 13 points and the Islanders (5-10, 2-0 Southland Conference) outshot the Golden Eagles (7-8, 1-1) from the field 48.1 percent to 42.6 percent.
The lead changed hands five times before Thomas hit a layup at 9:59 and Hameed Ali followed with a jumper to put the Islanders up 20-16 and they kept Oral Roberts at arm's length for a 37-31 halftime advantage.
The Islanders opened second half with a 10-3 run and a 44-34 lead in which Pye made a layup and back-to-back 3-pointers. Oral Roberts stayed close and cut the lead to six points on a Shawn Glover layup with 3:14 to go, but got no closer.
Glover paced Oral Roberts with 21 points and Korey Billbury added 18.