Outlaw banked in a 14-footer with 13 seconds left to complete Portland's comeback, and the Trail Blazers beat the Memphis Grizzlies 96-93 on Tuesday night.
Roy, who scored 13 of his 24 points in the fourth quarter, stole the ball from Memphis guard Mike Conley with 8 seconds left, then hit the ensuing two free throws to preserve the win.
"I guess I got credit for it," Roy said of the steal. "But he kicked it off his foot right to me."
O.J. Mayo's 3-point attempt as time ran out bounced off the rim, giving Portland its fifth victory in six games. The loss snapped Memphis' four-game winning streak.
The victory left Portland a game ahead of the New Orleans Hornets for the fifth seed in the Western Conference. The Hornets beat Miami 93-87 in overtime on Tuesday night. The Trail Blazers are only a half-game out of the fourth spot and home-court advantage in the first round. The Houston Rockets held on to that spot by defeating Orlando 93-83 on Tuesday night.
"This is new for us, clinching the playoffs with seven games left," Roy said. "We're just trying to figure out how to compete and play and stay motivated."
"We got lucky," said Portland coach Nate McMillan, whose team trailed by as many as 18 late in the first half.
Memphis had played well through most of three quarters, but the problems arose late in the third. Through the first three periods, Portland was shooting 43 percent. The Trail Blazers connected on 65 percent as they rallied in the fourth, hitting 13 of 20 shots, including 5-of-8 from Roy, and Outlaw connected on all four of his attempts.
"It really wasn't our offense, it was our defense," Memphis coach Lionel Hollins said. "We broke down on the pick-and-roll defense a couple of times, and they got wide open layups."
Portland took a 77-76 lead when Outlaw connected on a 19-footer with 8 minutes left, but Mayo hit consecutive 3-pointers as Memphis retook the lead with 6:58 left.
There were two ties and five lead changes in the fourth, the last coming when Outlaw banked in the 14-footer off an inbounds play.
"I just came to the ball, and I was trying to get something," Outlaw said. "Then I heard the whistle and I threw it up."
The teams were tied at 21 after a quarter, and Memphis held a 29-28 lead with 7:20 left in the half. At that point, the Grizzles rattled off 13 straight points, part of an 18-1 run that put Memphis up 47-29.
Memphis outscored Portland 26-14 in the second, but Aldridge connected on a three-point play and Roy's 3-pointer closed the half as the Trail Blazers cut the deficit to 47-35 at the break.
The Blazers, who average 12.8 turnovers, had a dozen by halftime and were shooting 33 percent. They finished with 19 miscues in the game.
"We were just in a fog," Roy said of the first-half play.
The Trail Blazers chipped away at the Memphis lead, getting it under double digits in the early stages of the second half. But Portland was still plagued by shooting and ballhandling woes, and couldn't get closer than nine until consecutive 3-pointers by Fernandez.
Sergio Rodriguez hit a pair of free throws, capping Portland's 10-0 run to end the quarter. Aldridge had 10 in the period, helping the Trail Blazers enter the final quarter trailing 69-67. Outlaw extended the rally with a 19-footer to open the fourth, pulling Portland even at 69.
"Their shooters started to heat up a little bit," Conley said. "They got a lot of good looks. In the first half, they were missing a lot of good shots, but in the second half, they started making them."
Down the stretch, Roy scored eight of Portland's final 10 points, only Outlaw's bank shot interrupting the streak.
The Trail Blazers are 31-6 against teams under .500, including 12 straight wins. With the San Antonio Spurs and Los Angeles Lakers looming the rest of this week, Portland could not afford to let a game with lowly Memphis slip away.
"We needed this game," Roy said. "It's important that we play to compete and play hard, and things like the playoffs and clinching and seeding won't matter."
Memphis was trying to win five straight for the first time since the end of the 2005-06 season. The Grizzlies are now 11-23 under Hollins, who took over when Marc Iavaroni was fired earlier in the season. The Trail Blazers are 31-6 against teams under .500, including 12 straight wins. The Grizzlies dressed only 10 players for the game. In addition to C Chris Mihm and G Mike Wilks, who haven't played since they were acquired in February trades, G Quinton Ross missed his second straight game with strained left quadriceps. Darko Milicic also did not play because a strained right hamstring. Portland has won seven straight over Memphis.