The superstar playmaker injured her right knee in the first half of last Thursday's win over Cronulla, with the Roosters confirming the worst possible prognosis on Monday.
It means Aiken, one of the NRLW's best players, will book in for reconstructive surgery and miss the remainder of the undefeated ladder leaders' season.
The Australian international will also be unavailable for the post-season Pacific Championship series and is no certainty to be fit for the start of the 2026 campaign.
"Tarryn is a highly influential player and such an important member of our squad, so this news is really tough for her and for all of us," said coach John Strange.
"She has been in terrific form and is a real leader on and off the field. While it's a setback, and we're all shattered for Taz, we know how driven she is, and we'll be supporting her every step of the way through her recovery."
The NRLW season is shaping as a two-horse race between the Roosters and second-placed Brisbane, whose only loss has come to the Roosters.
The Roosters have advanced automatically to a grand final qualifier and will face the winner of the week-one final between Newcastle and Gold Coast.
Corban Baxter is a chance to replace Aiken in the Roosters' 17 as she nears recovery from an ankle injury.
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