Roy, last season's Rookie of the Year, admittedly hasn't played well for the past two games.
"It's tough for me, but I've got to play through it and play through it," Roy said. "I don't think it's mechanics. It's confidence more than anything else."
Portland has lost seven of its last eight games, including an 85-74 loss to the Orlando Magic on Monday. The Blazers have lost eight straight to the Pacers overall.
Down by as many as 12 points and booed by the home fans in the third quarter, the Blazers narrowed it to 69-68 on Joel Przybilla's dunk. Outlaw's free throw tied it.
After Outlaw blocked Kareem Rush's shot, Sergio Rodriguez hit a 3-pointer to give the Blazers the lead and it stayed close the rest of the way.
The Pacers were coming of a 112-110 victory at Denver the night before. Dunleavy scored 30 points, two shy of his career best.
"On a back-to-back after a great win last night in Denver, we get a great third quarter and then Jamaal hits some big shots down the stretch," O'Brien said.
The Blazers went up by as many as nine points early in the game, after Roy's 3-pointer and consecutive layups from Outlaw made it 22-13 in the first quarter.
The Pacers kept up and Dunleavy tied it at 31 with a 3-pointer and Tinsley made a pair of free throws to put Indiana ahead.
The two teams traded the lead back and forth until Roy's tip shot made it 44-40 for the Blazers. After Dunleavy made a layup to narrow it, Aldridge hit an 18-foot jumper to give the Blazers a 46-42 lead at the break.
The Pacers went on a 17-0 run in the third quarter, capped by Tinsley's layup that made it 57-49. The crowd at the Rose Garden booed the home team.
Granger's 3-pointer made it 67-55 for the Pacers at the end of the quarter.
Indiana outscored Portland 25-13 in the third quarter.
"Tonight it wasn't the stretch that hurt us, it was the third quarter," Blazers coach Nate McMillan said. "We had so many open looks and just didn't knock them down."
Outlaw went flying into the cameramen at the base of the Blazers' basket after he was apparently pushed by Indiana's Foster. Outlaw charged back, but was pulled away by a referee. Foster was penalized with a technical foul. ... It was Blazer rookie Taurean Green's birthday. ... Tinsley was just 4-of-16 from the field. "I missed some shots, but I can't keep my head down. I've got to continue to play," he said.