Roy scored 10 of his 28 points in the fourth quarter and the Trail Blazers avoided a second straight collapse by holding off New Jersey 102-93 on Tuesday night.
The win came just two days after Portland squandered a 25-point lead and lost in overtime to Utah.
"It was good to see our guys tonight not allow that to happen," Portland coach Nate McMillan said. "I heard them talking. The last game against Utah pretty much everyone was on their own, not saying anything. They weren't going to allow this game to slip away."
Roy was the big contributor down the stretch, scoring six points on three consecutive possessions after New Jersey got within five points.
However, even he was well aware about the possibility of coughing up another much needed win.
"Yeah, it was a quick second thought about it," he said. "We dealt with it. It was something that was on the back of all of our minds. We did a great job tonight of holding a team off that was playing pretty loose and at home."
LaMarcus Aldridge added 27 points and Andre Miller had 20 as the Trail Blazers also overcame a sprained right ankle to recently acquired center Marcus Camby in snapping a two-game losing streak and winning for only the sixth time in 14 games.
The victory, coupled with New Orleans' loss to Cleveland, gave the Trail Blazers a two-game lead in the race for the final playoff berth in the Western Conference.
X-rays of the ankle were negative and Camby is day to day.
Courtney Lee and Devin Harris led the Nets with 28 points apiece. The total matched Lee's career high set earlier this season, and was a season high for Harris.
"It's frustrating because of the effort to fight back," Lee said. "If we started the game like that, it would have been a little different. But once you are down by so much and you are giving it you're all to come back, it takes a lot out of you."
The loss was the fourth straight for New Jersey, which set a franchise record with its eighth consecutive home loss.
The Nets, who blew an 18-point first half lead in a loss to Memphis on Sunday, rallied from a 21-point deficit by shooting almost 77 percent from the field in the third quarter.
Lee (11) and Harris (10) were the catalysts combining for 21 points on 8 of 10 shooting. The 33-point quarter got New Jersey within 77-70 entering the final quarter.
New Jersey closed to within five points four times in the final 6:11, but Roy answered the first three times, hitting two of three free throws, a baseline jumper and drive, the last one with 3:57 to go for a 93-86 lead.
"I really didn't want to lose this game and feel like I didn't give my best," said Roy, who was 9 of 14 from the field and 10 of 13 from the free-throw line.
Harris hit two free throws to close the gap to 93-88 with 3:45 to go, but Miller nailed a 3-pointer and Roy made two free throws after Harris hit a drive for a 98-90 lead.
"We got it down to five, but they responded and he [Roy] really made a difference," Harris said. "We just didn't have enough in the tank."
The only basket the Nets hit after that was a three-quarter court 3-pointer by Lee at the buzzer.
Portland was dominant in the first half, shooting nearly 59 percent in taking a 56-37 lead.
Roy scored 12 points in the first quarter to help the Trail Blazers build a 32-22 lead and Aldridge had 10 in the second to push the advantage to 56-37.
Camby, acquired on Feb. 16 from the Los Angeles Clippers for Steve Blake, Travis Outlaw and cash considerations, was hurt when Nets center Brook Lopez (17 points, 10 rebounds) stepped on his ankle as both waited for a rebound with 6:47 left in the first quarter.
Ironically, the last time Camby played here with the Clippers on Jan. 27, he also didn't get out of the first quarter. He bruised his ribs and left after seven minutes.
Portland has already lost centers Greg Oden and Joel Przybilla for the season with injuries.
Aldridge has scored at least 15 points in 18 straight games. ... Nets starting small forward Jarvis Hayes missed the game with a strained left calf. ... Harris picked up four fouls in the first half and none in the second. ... Harris knocked referee David Jones into the front row of seats late in the fourth quarter going for a loose ball. ... Portland has five straight against New Jersey.