Matthews, subbing for the injured Roy, scored a career-high 30 points, 22 in the first half, and the Trail Blazers beat the Memphis Grizzlies 100-99 on Tuesday night.
"He did exactly what we needed," Portland coach Nate McMillan said. "He scrapped defensively. I thought he let the offense come to him. It was good to see him knock down some shots and get to the basket."
Matthews shot 11 of 19 from the field, including 5 of 10 from 3-point range, in his first start of the season as the Trail Blazers salvaged a win after losing their first two games on a three-game road trip. Portland beat Memphis for the eighth straight time on the road.
"We all had to step up," Matthews said. "I'm part of a team, so I'm just fulfilling my duty as a teammate to step up like everyone else did."
"I was trying to get a little bit more assertive," Miller said of his fourth-quarter play. "I had a lot of shots early, but I didn't take them. It was an idea of keeping guys involved, and it fell our way."
Rudy Gay led Memphis with 20 points, while Zach Randolph had 19 points and 14 rebounds. O.J. Mayo scored 17 and Mike Conley added 16, including a 3-pointer at the buzzer that wasn't enough to send the game into overtime.
Roy, the Trail Blazers' leading scorer with 18.1 points per game, missed his first game of the season with a sore left knee.
"You got to give them credit. They've got a star player out, and they played good," Randolph said.
The teams exchanged the lead throughout much of the fourth period, neither holding more than a two-point advantage until 6 minutes remained, when Matthews made consecutive baskets for an 83-79 advantage. There were 14 lead changes and a trio of ties in the fourth quarter alone.
A tip-in by Nicolas Batum (11 points), then a steal by Miller that led to his 10-footer with 21 seconds left gave Portland a 97-93 lead, and there would be no more lead changes.
"Everyone is taking away the inside with either zone or doubling up," Memphis coach Lionel Hollins said of the Grizzlies offensive woes. "We just have to figure out how to attack better without forcing it inside, and we've got to make shots. When we are on the perimeter, we have to make shots."
Portland relied on 3-pointers to take an early lead while Memphis struggled from the field. The shooting eventually would even out, although the Trail Blazers would end the half 6 of 11 from outside the arc. Matthews already was more than sufficiently making up for the lost offensive production with Roy out, scoring 22 in the first half, on 7 of 10 from the field.
"We knew he was ready to play," Miller said. "He brings a lot of energy to the game. He made some good plays offensively and defensively. He has the experience. That's what we expect of him. It's a collective effort, but tonight was his night all around."
Portland led 51-45 at halftime as Aldridge added 14 points.
Memphis chipped away and Greivis Vasquez converted a three-point play with 8.9 seconds left in the third period to cut the Portland lead to 71-70 entering the fourth.
But Memphis couldn't make plays down the stretch.
"We needed to play well and to give ourselves something good going home," McMillan said. "Now, we need to go home and take care of business there.
"We had two bad games. We weren't playing well on either end of the floor. So, we'll take this and try to build off of it."
Randolph's flagrant-1 foul against Kevin Garnett in Saturday's overtime loss to the Boston Celtics was rescinded by the league earlier Tuesday. The Trail Blazers now return to the Rose Garden for a three-game homestand. Miller has played in 624 consecutive games, the longest such streak in the league. Gay had two steals. His swipe in the first quarter gave him 417, passing Shareef Abdur-Rahim for second place on the franchise list. Shane Battier holds the Grizzlies' top spot with 507. Memphis' last win over the Trail Blazers at the FedExForum was Dec. 21, 2005.