An early try under the post showed the Raiders were here to play with Dunamis Lui scoring first.
But the Roosters hit back with Brett Morris claiming the 161st and 162nd tries of his career with a brilliant double in the corner.
In a sign the Raiders aren't going to go quietly for the rest of the season, Canberra hit back in the first couple of minutes of the second half with Jarrod Croker grounding a grubber to tie it up at 12-all.
In a game that had everything, it even had some bad blood with a tackle from Josh Papalii on Angus Crichton leading to some pushing and shoving.
The Roosters' Crichton had accidentally — or carelessly or maliciously depending on who you ask — elbowed the Raiders prop in the nose, which he didn't take too kindly to.
Some were shocked that the penalty went Sydney's way.
Crichton then also got the penalty with Kyle Flanagan kicking the Roosters into the lead 14-12.
The Raiders responded as halfback George Williams did it all himself, before Josh Morris threw a flick for Matt Ikuvalu to score his first of the night — and sixth in the last two games — before Flanagan kicked a sideline conversion to make it 20-18 with 20 minutes remaining.
With the game on the line and predictions the Raiders would need to keep it low scoring and close blown out of the water, Papalii hurt the Roosters more than an elbow on the nose — hitting a short pass from Williams and running untouched 25m to the line to snatch back the lead 24-20.
It was a perfect run from Papalii, breezing to the line and scoring the winning try.
The Roosters tried to hit back but poor handling mixed with a couple of forward passes saw the Raiders hold on for a famous win.
Another downside for the Roosters was a suspected medial cruciate ligament strain for Crichton, who came from the field late.
Papalii, who ran for over 200m in 18 runs and had 31 tackles in his 55 minutes on the field, was named man of the match. He was pumped by the performance especially with so many forwards injured.
"It was awesome (scoring three tries under the posts) we sort of just went back to basics with our game plan and it's working at the moment and hopefully this is the start of something special," he said.
Channel 9's Andrew Johns called Papalii "absolutely incredible" as he led the way up front for the Raiders.