Roy played six seasons in the National Basketball Association (NBA) for the Portland Trail Blazers and Minnesota Timberwolves.

[2][3] On December 10, 2011, Roy announced his retirement from basketball due to a degenerative knee condition,[4][5] though he returned in 2012 to play five games for the Timberwolves.

[11] He first started taking basketball seriously while playing for the Amateur Athletic Union, one of the largest sports organizations in the United States.

His parents and his older brother had not attended college, and due to a learning disability, Roy had difficulty with the SAT; his reading comprehension was slow, which increased the time he needed for tests.

Unsure whether he would be able to attend a four-year college, Roy worked on the Seattle docks, cleaning shipping containers for $11 per hour.

[19] During his senior year, Roy averaged 20.2 points per game while leading the Huskies to a 26–7 season and a second straight Sweet Sixteen appearance.

[20] Roy was named Pac-10 player of the year and received All-American honors at the end of the season, while also being a finalist for the Wooden, Naismith, Oscar Robertson, and Adolph Rupp awards.

[17] Roy had a 2006 pre-draft workout with the Trail Blazers prior to being selected by the Minnesota Timberwolves as the sixth overall pick.

[7][21] On January 22, 2009, before a University of Washington Huskies home game versus the USC Trojans, his number 3 uniform was retired.

[24] An impingement in his left heel kept him out of 20 games early in the season, but he scored his first career double-double shortly after his return, on December 22, 2006, against the Toronto Raptors.

Roy missed several weeks of action because of the rehabilitation, but was ready on the opening day of the season against the Los Angeles Lakers.

[29] On November 6, against the Houston Rockets, Roy hit a game-winning 30-foot jumper in overtime with eight tenths of a second left.

Roy was again selected as a reserve in the 2009 NBA All-Star Game, where he scored 14 points in 7-for-8 shooting, grabbed 5 boards, and dished out 5 assists in a game-high 31 minutes of action.

[36] On August 5, 2009, it was confirmed that Roy had agreed to a four-year maximum-salary contract with a fifth-year player option, keeping him a Trail Blazer until at least the 2013–14 season.

Roy underwent surgery on April 16 and was expected to miss at least the first round of the 2010 NBA playoffs, but returned for Game 4 after eight days of recovery time to lead the Blazers to a win.

[44] He returned to the lineup on February 25, scoring 18 points off the bench, including a clutch three-pointer to force overtime, and helping the Blazers defeat the Denver Nuggets 107–106.

In the fourth quarter, Roy scored 18 points after going 1-for-3 the previous 3 quarters, including a clutch 4-point play to tie the game and a bank shot from the middle of the paint with 49 seconds left to give his team the lead for good, finishing with 24 points to lead the Blazers to an improbable 84–82 win to tie the series.

Roy reportedly had expressed interest in signing with the Dallas Mavericks, Golden State Warriors, Minnesota Timberwolves, Indiana Pacers, or Chicago Bulls.

[52] The deal put Roy with All-Star forward Kevin Love and point guard Ricky Rubio.

"[55] After ending his playing career, Roy joined Nathan Hale High School as the head coach of the boys' basketball team in 2016.

[56][57] In March 2017, he received the Naismith National High School Coach of the Year award after his team posted a perfect 29–0 record during the regular season.

[61] Roy's longtime girlfriend Tiana Bardwell delivered their first child, Brandon Jr., whom they nicknamed BJ, on March 27, 2007, in Seattle.

[65] On April 29, 2017, Roy was shot and received non-life-threatening injuries while attending a party at his grandmother's home in Compton, California.