The NSW halfback scored just before halftime and iced the result with two four-pointers in the last eight minutes at Allianz Stadium.
However, the win didn't come easily for the hosts, who conceded two second-half tries while winger Joseph Leilua was in the sin bin for a professional foul.
Leilua gave his side the lead midway through the opening stanza when he waltzed through the Dragons defence for his sixth try of the season and Pearce doubled the lead when he raced under the posts on the stroke of halftime.
Braith Anasta kicked his third goal four minutes after the interval to put the Tricolours 14-0 in front.
But as they have so many times this season, the Roosters shot themselves in the foot when Leilua dived on top of Chase Stanley to prevent a quick play-the ball, after the centre was chased down by Brad Takairangi, and was sent off for 10 minutes.
The Dragons took full advantage, Matt Prior diving over from the resulting penalty, and Ben Creagh showed great handling skills to haul in a Nathan Fien kick and bundle over.
However, Steve Price's men, who are the lowest scorers in the competition, were unable to add to the total when Leilua returned, with Brett Morris being denied two certain tries due to forward passes from Jason Nightingale and Nathan Green.
With the Roosters' fans in the crowd of 12,528 feeling the nerves, exciting young winger Roger Tuivasa-Sheck showed why he is rated so highly by coach Brian Smith when he ran the ball 40 metres from his own in-goal area and offloaded to Pearce who cruised to the line.
Anasta added the extras before Pearce scored his third three minutes from time.
Smith was full of praise for Pearce's performance and said the NSW playmaker had only just recovered from the exertions of Origin and that showed in his display.
"I just called him Usain - it's the fastest we've seen him move for a while," Smith said.
"He was right on the ball all night. I think most of us underestimate how hard it is.
"I watched plenty of guys over the years who have played for me and for other clubs. The aftermath of Origin is immense.
"Players are shattered physically and mentally and he is only just working out how to deal with it."
Dragons' coach Price lamented his side's errors and felt his players handed the win to the Roosters, which all but ended their hopes of reaching the finals.
"They were there to be beaten," Price said.
"But through our lack of execution at times, we had two forward passes that could've led to tries if we executed them properly."