Up 26-10 with 30 minutes to play, the Roosters all of a sudden appeared gone when Tyrell Sloan turned it on for the Dragons to help them level at 26-26.
The Red V then seemed favourites to win when Victor Radley was sin-binned for a high shot, after what initially appeared to be head-on-head contact with Michael Molo.
Radley's third sin-bin in three games prompted Roosters captain James Tedesco to accuse referee Adam Gee of bias, before the Tri-colours held firm without their lock.
Ashton Collier Medal recipient Keary then nailed the field goal with six minutes to play, in the first real test of the Roosters' new-look attack with Joey Manu in the halves.
The win did come at some cost though, with winger Daniel Tupou suffering a hamstring injury that could have serious ramifications for NSW and their State of Origin selections.
After a week of talk around Sam Walker's axing and Manu's move to the halves, the Roosters' attack looked the most fluent it has been all season in the first half.
Against a Dragons defence that was parting through the middle, Keary scored one try when he dummied his way over from close distance and Radley starred.
One came when the lock went to the line and put Egan Butcher through a hole for Tedesco to score, while Radley scored another off a great Jared Waerea-Hargreaves face ball.
Manu also justified his move to five-eighth and getting closer to the ball when he scored another four-pointer after the break, running the ball after a Keary pass on the last and dragging two over the line.
At that point it was 26-10 and it looked as if the Roosters would run away with it and put on a score.
Enter Sloan.
The fullback first stepped pass Joseph Aukuso-Suaalii and Keary and put on a flick pass for winger Tautau Moga to cross.
From the next set he put Moses Suli into a hole and then loomed up on the inside to step Jaxson Paulo and go in under the posts.
Moments later he handed off to Suli, who fended off two Roosters on the spot and found Moga to get the ball down for his third try.
Sloan then missed a chance to take the lead for the Dragons when he couldn't collect a Talatau Amone grubberkick as he charged onto it close to the line.
But it was the experience of Keary and Joey Manu who came up with the winning play when the latter ran out of dummy-half, went back to his halfback and watched him knock over the field goal.
The result left the Dragons 13th on the ladder with two wins and five losses, as further pressure is heaped on off-contract coach Anthony Griffin.
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