Former Raptors star Tracy McGrady, bothered by a sore left knee, was held to four points on 2-for-9 shooting.
"I got a little frustrated at times," McGrady said. "It's kind of hard to get in the groove when you're only touching the ball once every five minutes."
McGrady started but said he will skip Saturday's game at Atlanta and is only expected to play every other game during a stretch of three back-to-backs over the next nine days.
Bosh scored six straight points as Toronto ended the first quarter with a 14-2 run to open a 25-14 lead. Houston cut it to 31-30 with 6:32 remaining in the second, but Bargnani scored eight straight points for the Raptors to build a 48-38 lead at the half.
Bargnani opened the third quarter with five more points, part of a 9-2 run that gave Toronto a 57-40 advantage.
"He's been playing well," Bosh said of Bargnani. "He's taken the challenge on defense and on offense. He's doing a good job."
Houston shot 4-for-22 in the third, scoring only 10 points, and trailed 69-48 heading into the fourth.
Already without forward Jermaine O'Neal, who missed his second straight game with a sore right knee, Toronto lost guard Jose Calderon to a strained right hamstring early in the second quarter.
"Nobody expected us to win tonight," Bosh said. "Not only did we win, we won in convincing fashion."
Calderon, who came in third in the NBA with 9.0 assists per game, sustained the injury while driving to the basket late in the first. Calderon returned in the second but lasted just a few possessions before signaling to the bench for a substitution. He is day-to-day.
For Calderon, who missed two November games with the same injury, it was the first time he failed to record an assist since a 102-98 win at Indiana last Feb. 25, a stretch of 57 games.
Toronto had not lost five straight at home since March 29 to April 9, 2006. ... The Rockets were 7-for-27 from 3-point range. ... All of Wafer's points came in the fourth. ... Houston forward Shane Battier (sore left foot) missed his second straight game, and is expected to miss at least five more. ... Former NFL quarterbacks Doug Flutie and Jesse Palmer attended the game.