Austrian Dominic Thiem fared less well, with the the second seed being bundled out 4-6, 7-6, 6-4 by American Steve Johnson in the late match on centre court.
But third seed Raonic, who was forced to sit out the US Open due to persistent problems with his left wrist, displayed very few signs of rust after a seven-week absence and took just 71 minutes to blast his way into the last 16.
Troicki fought gamely but when a Raonic volley clipped the net and trickled over, the Serb slammed his racquet to the ground in disgust and bellowed furiously at courtside spectators.
Raonic, a former world number three and winner of eight ATP Tour singles titles, rifled 16 aces to pile the misery on Troicki, completing victory with a kicking serve that his opponent could only waft into the net.
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"It was a good match for me in a lot of ways -- disciplined, competed well -- considering the circumstances," said Raonic.
Currently ranked 12th, Raonic finished runner-up at the Japan Open three years running from 2012-2014 -- twice to local favourite Kei Nishikori.
The former Wimbledon finalist next faces Japan's Yuichi Sugita, who progressed after 2015 Tokyo runner-up Benoit Paire of France threw in the towel upon losing the first set 6-4, citing fatigue.
A late decision to rush the net failed to save Thiem, who wilted after losing the second-set tiebreak 7-5, and Johnson closed out an upset win with a fizzing body serve after two hours and 18 minutes.
Frenchman Richard Gasquet, another former Japan Open finalist, upset American sixth seed Sam Querrey 6-4, 7-6 after clinically winning the second-set breaker 7-2.
In other matches, eighth seed Diego Schwartzman of Argentina beat American Donald Young 6-2, 7-5 while Australia's Matthew Ebden ousted big-serving Croat Ivo Karlovic 6-4, 6-3.
Croatian Marin Cilic heads the Tokyo field this year at a tournament whose list of former champions includes tennis greats Ken Rosewall, John McEnroe, Pete Sampras, Roger Federer and Rafael Nadal.