Execution issues haunted both sides on Saturday night and ensured a tight first half but the Storm pulled it together in the second, winger Xavier Coates notching a hat-trick of tries to put the game beyond doubt.
To finish the season with a winning record, the Roosters must now claim six of their final seven games and even that might not be enough to guarantee a top-eight berth.
The Roosters' points differential of 108 compounds their woes but they will take comfort from finishing last season on an eight-game winning streak that confirmed a similarly unlikely finals berth.
The Storm, meanwhile, have won four of their past five games and could finish the weekend as high as third on the ladder.
Preparations for the Women's World Cup forced the Roosters back to the SCG for the first time since the completion of their new home ground Allianz Stadium late last season.
But the Tricolours could not conjure the clinical best of their recent four-year stay at the sacred ground, struggling all night to turn opportunities into points.
The Storm were similarly disjointed in the first half.
Their only try of a 6-4 first 40 minutes came when Coates intercepted a Sandon Smith cut-out pass and ran 90 metres to the tryline.
With Roosters captain James Tedesco rested following State of Origin duty, five-eighth Luke Keary took charge and scythed down the left on a break that helped the side hit back through Daniel Tupou.
Tupou crossed again in the final minutes and joined Anthony Minichiello as the most prolific tryscorer in Roosters history with his 139th four-pointer.
But that was the only high point for the Roosters.
The Roosters had all the ball in the 10 minutes after halftime but when they could not capitalise, the Storm were primed to punish them.
Jahrome Hughes ran an explosive line to the right of the goalposts to give the Storm their second try, and in the next set, Cameron Munster's kick found Coates on the left and confirmed his double.
It was much the same Munster-to-Coates play that handed the Queensland representative his hat-trick.
Ex-Storm hooker Brandon Smith made an incident-free return from a thumb injury via the bench and made 23 tackles.
Repeat offender Victor Radley was placed on report for raising his elbow on Munster as the Storm five-eighth made a tackle and teammate Jared Waerea-Hargreaves could join him on the charge sheet for tripping Grant.
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