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.
Maryland point guard Melo Trimble has withdrawn from the NBA draft and will return to College Park for his junior season, sources told ESPN.
Louisville's Chinanu Onuaku, who recently underwent a medical procedure to correct a heart rhythm issue detected during the combine, will keep his name in the NBA draft pool.
Andrew White III will return to the Nebraska men's basketball team next season after removing his name from the NBA draft.