Playing in his hometown tournament for the first time since cracking the world's top-25, Raonic was not at his best but held serve throughout the 69-minute match while a rowdy crowd waved red signs with "Go Canada" splashed across in white letters.
"I'm proud with the way I competed, with the way I played, I did a lot of important things well but I have some space for improvements for my next match," Raonic said.
"I was pretty fluid and relaxed most of the match ... but I got a bit sloppy, maybe trying to force a little bit too much in the last few return games on his serve, and I was making some sloppy errors and giving away too many points at that point."
The big-serving 21-year-old, who will join forces with Troicki for a doubles match on Wednesday, broke his opponent in the eighth game of the opening set for a 5-3 lead and remained in relative control the rest of the way.
The match was Raonic's first since his 6-3 3-6 25-23 loss to Frenchman Jo-Wilfried Tsonga last week in what was at the time the longest three-set match in Olympic tennis history.
Raonic, who as the tournament's 16th seed had a first-round bye, will play the winner of Wednesday's match between Murray and Italian qualifier Flavio Cipolla for a spot in the quarter-final of the tournament.
Isner, playing his first match since losing to world number one Roger Federer in the quarter-finals at the London Olympics, needed one hour and 48 minutes to secure a 7-6 7-5 victory over a plucky Pablo Andujar of Spain.
Andujar, the world number 44, managed to frustrate Isner by chasing down an array of shots but ultimately ran out of answers as Isner, who recorded 17 aces, relied on his power and his big serve to advance.