Another masterful display from superstar No.1 Tamika Upton helped the Knights go top of the league, the fullback scoring two brilliant tries and running for 203m in a player-of-the-match performance.
It was just the Roosters' second loss of the season and snapped their run of five straight wins as reigning premiers Newcastle reminded the competition of their might.
Upton started the show when she grubber-kicked for herself and gathered the ball to score, before adding another in the second courtesy of a perfect one-two with back-rower Yasmin Clydsdale.
A slicing 60m kick return from Upton soon after was capped by winger Jasmin Strange, before teen phenom Jesse Southwell slalomed her way through Sydney defenders and crossed in the dying stages.
But it was the defensive attitude that caught the eye of Newcastle coach Ronald Griffiths after his side shut down the usually lethal Roosters attack.
"We were clunky at times in attack, although there were some really good individual performances ... we didn't quite nail execution," he said.
"But we've built the last four weeks on being able to be a great defensive unit and I think we've seen that today.
"(Upton) was playing what's in front of her and seeing some opportunities and she's so talented she can capitalise."
The Roosters missed star prop Millie Boyle who was a late out with a shoulder injury, joining centre Jessica Sergis on the sidelines after she had finger surgery.
Earlier, Brisbane fought back late to cling to one of the box seats in the race for finals with a 22-18 win over Wests Tigers in Newcastle.
Shenae Ciesiolka's 67th-minute try completed an impressive come-from-behind win for the Broncos, who had looked in massive trouble trailing 16-6 early in the second half before finding the last three tries of the contest.
The loss ruled the Tigers - along with Cronulla and St George Illawarra - out of finals contention with one round of the regular season remaining, and reduced the race for the top four to five teams.
Canberra need to beat North Queensland on Sunday to keep their chances alive.
Whatever happens in that match, Brisbane would seal finals by beating the Dragons next weekend.
The Broncos' comeback started with a bursting try for prop Brianna Clark, while they tied the score behind hooker Destiny Brill's dummy-half dive after a big run from Chelsea Lenarduzzi put them in scoring position.
Smart play from halfback Ali Brigginshaw allowed Ciesiolka to get over late and seal the vital win.
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