Koroisau was sent to the bin by referee Ashley Klein midway through the first half of Thursday's win for an apparent hip-drop tackle on Canberra forward Noah Martin.
He was also placed on report for a dangerous throw early in the second half.
The Tigers hooker has already paid $5800 in fines after being hit with three separate dangerous-contact charges this season.
Koroisau will learn his fate on Friday, and a lengthy suspension could cruel the creative dummy-half's bid to return to the NSW squad for the first time since 2023.
"Where's he supposed to go? He's coming from behind, making a cover tackle, where he has to tackle his legs," said Tigers coach Benji Marshall.
"That's where he's going to end up, so don't think it was intentional.
"He did his 10 minutes. Surely that's enough."
Marshall's side claimed their fifth win of the season with victory in front of 17,153 at Leichhardt Oval on Thursday.
Fullback Jahream Bula failed to finish the game because of a shoulder injury.
"He hurt his shoulder last week, but it's not worse than last week ... he seems to tell me he'll be confident for next week," Marshall said.
The Raiders could find themselves in trouble after a first-half mix-up led to debutant Daine Laurie briefly entering the field of play and giving Ricky Stuart's men 14 players.
Laurie had no involvement in the play as he was substituted on for Ethan Strange, who overcame an ankle injury to return in the second half.
Laurie was thrown on as Koroisau set up the Tigers' first try by putting in an improvised last-tackle kick to the Raiders' in-goal that sat up perfectly for left winger Luke Laulilii.
Strange limped off after Laulilii's try to thrust Laurie in for his first Raiders appearance at NRL level, with the Tigers extending their lead when Adam Douiehi ran over Canberra halfback Ethan Sanders.
But Koroisau's 27th-minute sin-binning opened the door for Canberra, who got on the board when Matt Timoko charged back in-field.
Strange came back on just before Kaeo Weekes crashed over, with Sanders' two conversions pushing the Raiders ahead.
The halfback kicked a penalty goal from right in front to make it 14-10 at the break.
But the Raiders could not hold on to their lead and failed to score a point after halftime.
"They can start booking their end of season holidays a lot earlier if we don't start fixing our errors," said Raiders coach Stuart.
"We put ourselves in a position to win the game."
Taylan May crossed first before Doueihi and Laulilii scored their second tries of the night, before Bula went off injured.
The Raiders were unable to mount a comeback and slumped to a 3-5 start, with a Doueihi field goal and a late Royce Hunt try sealing victory for the Tigers.
