Summers, with 22 in the first half, finished 10 of 19 from the field, including five of 10 from three-point range. The Rebels struggled from the field, 25 of 72 for 34.7 percent, but out-rebounded Troy, 53-38, led by Aaron Jones with 13.
The Rebels played without returning leading scorer Marshall Henderson, who sat out the first of a three-game regular season suspension.
Henderson is scheduled to miss the opening two games of the Southeastern Conference schedule in January after he was cited at a traffic stop for allegedly driving without proof of insurance.
Summers was decisive in the first half, hitting nine of 11 from the field and all three shots from three-point range. The offensive outburst was especially evident as his teammates were only seven of 32 from the field.
Troy challenged early, pulling to an 11-11 tie as Thomas capped a 6-0 run with a layup with 13 minutes remaining. The Trojans managed only two other field goals for the remainder of the half, finishing 7 of 22 from the field.
Ole Miss answered with an 18-2 run to build what became an insurmountable29-13 lead. Summers accounted for 15 of the points in the decisive surge as the Rebels built a 39-26 halftime lead.
The Rebels led by as many as 18 points in the opening five minutes in the second half, 51-33. Millinghaus, with 10 second-half points, hit a twisting layup with 15:46 left to provide the game's largest margin.
Troy pulled within 59-49 with 7:47 left on a jumper by Thomas, but failed to convert two ensuing possessions to get within single digits. Summers responded with a rare four-point play, converting the free throw after a three-point shot, for a 63-49 lead with 6:39 left and Troy never got closer than 12 points again.
Ole Miss improved to 8-0 against Troy and stretched their season-opening games winning streak to 10.