The sources told The Oregonian Roy's doctor told him he could not continue to play. Roy has had six knee surgeries.
"You can't do this," the doctor reportedly told him. "You might end up not walking."
The newspaper said one source described Roy as "emotional." The Trailblazers discussed having a news conference Thursday afternoon but decided to give Roy time to come to terms with his situation.
Roy, a star guard with the University of Washington Huskies, was drafted by Portland in 2006. He was named NBA Rookie of the Year for his first season and was selected as a reserve for the NBA All-Star Games in 2008, 2009 and 2010.
In last season's playoffs, Roy made 18 points in the fourth-quarter against Dallas, helping the Trailblazers, who had been down 23 points, win the game.