The 6-foot-8 Frenchman, in his second season, said McMillan told him to "just play defense first, then the offense will come."
"I let the game come to me," Batum said.
Chris Bosh had 28 points and seven rebounds for the Raptors, who have lost five straight, matching a season high.
Portland kept Toronto at bay, going up 101-93 on Roy's hook shot and a pair of free throws from Batum.
With 1:11 left, Batum nailed a 3-pointer that sealed it.
"He's going to get open shots just because who he's on the floor with," McMillan said. "It's just a matter of knocking those shots down. Tonight, he knocked those 3s down and he can continue to do that."
Portland held the eighth and final playoff spot in the Western Conference, five games in front of Memphis, and just a half-game back of seventh-place San Antonio and a game back of Phoenix.
The Raptors were also in the eighth place in the Eastern Conference, struggling while just a game up on Chicago.
"There no science to it. It's not rocket science or brain surgery. You just have to win," Bosh said. "If you make it complicated, it will be complicated. We just have to win games. That's all."
But the deal abruptly fell through and Turkoglu, who helped Orlando to the NBA finals last season, agreed the next week to join the Raptors.
Turkoglu was booed loudly during pregame introductions. Conversely, former Blazers guard Jarrett Jack received a warm round of applause.
Turkoglu then made a 3-pointer 19 seconds into the game.
But Aldridge got off to a quick start for the Blazers, with 10 points in the first six minutes, capped by a jumper that pulled Portland to a 15-all tie.
It was Rudy Fernandez who helped swing the game in Portland's favor in the second quarter. Fernandez had 10 points in 12 minutes, including three 3-pointers that put the Blazers up 45-35 midway through the second quarter.
He also had three assists, including a no-look, behind-the-back pass to Martell Webster, and an alley-oop to Aldridge that drew cheers from the Rose Garden crowd.
The Blazers led by as many as 14 points en route to a 60-49 lead at the break.
Turkoglu's 3-pointer with 1:16 left in the third quarter narrowed it to 83-76. But on the other end he fouled Fernandez, who made both shots.
Bargnani closed the Raptors to 85-80 early in the fourth quarter, but the Blazers responded and went up 91-80 after Batum's 3-pointer.
Bosh was playing in his fifth game after missing seven games with a sprained ankle and a stomach virus.
"I've had to have a few games to get back to my normal self," Bosh said. "It took a toll on us but that's the reality. We're just going to have to dig ourselves out of this hole and nobody can do it for us but ourselves."
The Blazers were coming off a 110-94 victory over the Sacramento Kings. Portland hosts the Wizards on Friday.
The Blazers have won four straight against the Raptors. Neither team had won more than three straight in series history. ... The Raptors return home from their 0-4 road trip to host Atlanta on Wednesday. ... All five of the Blazers' starters scored in double figures. ... Roy wore his No. 3 Washington jersey after the game. The current Pac-10 tournament champion Huskies are an 11th seed in the East region for the NCAA tournament and will meet sixth-seeded Marquette in San Jose, Calif., on Thursday.