A grade-one tripping charge attracts 75 demerit points which would make him available for the first week of the finals, however is in danger of spending time on the sidelines should he attract a higher grading.
By the 23rd minute, the Roosters were scoring at better than a point a minute after running in tries through Michael Jennings, Blake Ferguson, Boyd Cordner and Jake Friend for a 24-0 advantage.
Shaun Kenny-Dowall also made a strong return to the field after missing the previous seven weeks, coming up with some vigorous carries but was outshone by his right-side partner Ferguson.
Prop Sam Moa stepped up in Jared Waerea-Hargreaves' absence while Roger Tuivasa-Sheck was at his creative and elusive best.
The only thing that went wrong for the Roosters was when their numbers started falling off the back of their jerseys during the first half.
The Roosters finished the season two competition points ahead of Brisbane and will meet either Melbourne, Cronulla or Canterbury in week one of the finals.
They became the first side since Manly in 1995-97 to win three straight JJ Giltinan Shields and the first side in a united competition since the Sea Eagles of 1971-73.
The Rabbitohs' hopes of back-to-back premierships appear in tatters after they conceded their second big scoreline in consecutive weeks after being thrashed 47-12 by the Broncos eight days earlier.
Missing Greg Inglis - who is due back from a knee injury next week - John Sutton and Issac Luke, the Rabbitohs barely fired a shot and were badly shown up in defence.
Roosters coach Trent Robinson said it was the side's ability to perform without the likes of Waerea-Hargreaves and Pearce which put them in such good stead.
"That's why we finished first," Robinson said.
"It doesn't matter who plays. People will go out for Origin or injuries and they've just got to know that we trust them and they have a role to do ... there were a lot of questions about how would we go without Jared and without Mitch. But I sort of brushed them off.
"Not because I was trying to do the coach thing, but that's how much we believed in the players who were coming in."
South Sydney coach Michael Maguire said his side were still in the hunt for the title despite suffering three straight losses heading into the finals and conceding 77 points over the past fortnight.
Asked where his side were sitting heading into their elimination final, he said: "Pretty well exactly where everyone else is.
"There are eight teams left and there's an opportunity for every team that plays over the next four weeks.
"For us, we'll take plenty out of that second half. There are things in the first half that we'll look at but there's various things we know we're capable of doing."
- AAP
