Jack had told Roy several times that he was going to be in the corner during Portland's 100-91 victory over the Denver Nuggets Wednesday night.
"He kept telling me he was open but when I looked for him, it was like I was kind of open, too," Roy said.
Then, with 33.4 seconds left, Roy did pass to Jack -- who hit a 3-pointer that made it 94-88 and all but sealed it for the Blazers.
"It just made it better because I found him and he made that big 3 for us," Roy said.
Zach Randolph had 26 points and a season-high 17 rebounds in helping send the Nuggets to their fourth straight loss. Roy had 25 points and eight assists and Jack added 14 points and eight assists.
The Nuggets were without Allen Iverson, who sprained his ankle in Denver's 105-101 loss to Charlotte on Monday. He did not make that trip to Portland after playing 19 games since he was traded from Philadelphia.
Still, Denver cut a late 90-82 deficit to 91-88 on Marcus Camby's layup with less than a minute to go.
Jack answered with his 3-pointer to make it 94-88, but after Roy added a pair of free throws, Carmelo Anthony kept the Nuggets in it with a 3-pointer with 18 seconds remaining.
The Nuggets would get no closer, and Roy and Randolph closed out the game with four straight free throws.
The Trail Blazers have won four straight at home, but were coming off a 103-91 loss at the Hornets. The Blazers have won six of nine overall.
"The bottom line is it doesn't matter if it's Denver or anyone else, we've got to win, and we've got to win at home. We've got a nice little streak going here," Portland forward Ime Udoka said.
The Blazers go to Denver to play the Nuggets on Friday.
Anthony finished with 33 points for the Nuggets, who had 13 assists.
"With only 13 assists I don't think you'll win very many basketball games," Denver coach George Karl said. "You've got to make a lot more plays with each other than that. We took way too many forced shots."
Roy was selected earlier in the day for the rookie squad for the Rookie Challenge at All-Star weekend. Going into Wednesday's game, Roy was leading all first-year players with 14.5 points per game.
The Nuggets reclaimed the lead and stretched it to 35-30 on Anthony's layup with 3:57 remaining in the half. Denver held on for a 42-40 lead at the break.
Portland went ahead 59-56 on Jack's reverse layup and free throw, but Denver stayed close and Eduardo Najera's follow tied it at 66 at the end of the third quarter.
The Blazers went back up 77-71 on Martell Webster's 3-pointer with 8:04 left. Roy's 3-pointer made it 82-74. Randolph hit a key 20-foot jumper with 2:27 to go that put Portland up 90-82.
It was Randolph's 28th double-double this season.
The Nuggets prevailed 109-93 on Jan. 14 at the Rose Garden, but allowed Portland rookie Sergio Rodriguez 23 points and 10 assists. This time, Denver double-teamed Rodriguez at times.
Rodriguez rolled his left ankle badly late in the third quarter and left the game. X-rays on the ankle were negative.
Karl said it will help having Iverson back, which may happen as soon as Friday.
"Our penetration goes up 25 times a game," Karl said. "No one can stop him from going where he wants to go."
Before the game, the Blazers held a moment of silence for former chief scout and general manager Stu Inman, who died Tuesday. Inman helped build the Portland Trail Blazers' 1977 NBA championship team. Among those he drafted were Geoff Petrie, Jerome Kersey and Clyde Drexler. ... The Nuggets had won four straight in Portland.