The three-time All-Star is sitting out Monday night's game against the Oklahoma City Thunder and will miss Wednesday's regular season finale against Golden State on Wednesday night.
He will require surgery and will be out from four to six weeks. But he said he may try to play with the injury in the playoffs because doctors told him it cannot get worse.
"I want to play," Roy said. "It's the playoffs. You play 82 games and take a beating just to get to this point."
Roy is the Blazers' leading scorer with 21.5 points per game. He injured his knee on Sunday, 11 minutes into the Blazers' 91-88 victory at the Los Angeles Lakers.
"The minute it happened I knew something wasn't right," said Roy, who also tore his meniscus when he played at the University of Washington.
The Blazers have clinched a spot in the playoffs, but their opponent for the first round has yet to be determined.
Roy said doctors plan to re-evaluate his knee on Friday. He said that if he is able to play, he doesn't want to be a distraction for his team.
Thirteen different Blazers have missed a combined 305 games because of injuries this season, second in the league only to the Warriors and the most of any playoff-bound team.