In his first game since last July, Mitchell stood tall to drag a depleted Rabbitohs side off the canvas and snatch a famous win at Accor Stadium on Friday night.
Souths played the final 30 minutes with just 14 fit players after five-eighth Cody Walker, halfback Jamie Humphreys and winger Mikaele Ravalawa hobbled off with hamstring issues.
But in front of a crowd of 22,114 - and as his Bunnies trailed 14-8 with little more than a quarter of an hour left - Mitchell rose to the occasion against his former club.
An audacious goalline drop-out from Mitchell bounced in Souths' favour and led to Jye Gray's try under the posts, which made it 14-14 in the 64th minute.
Mitchell, filling in at five-eighth after being named to start at centre, then produced the play of the game to condemn the Roosters to a 1-4 start.
Rather than set up for a field goal attempt with 10 minutes left, he ran to the left and hit winger Isaiah Tass with a perfect cut-out ball that zipped past three Roosters players.
Tass tip-toed down the touchline to score and Mitchell converted to seal a Souths win that gives his side a 4-1 start under returning supercoach Bennett.
"He had to do something, he was kind of social loafing out there," Bennett said of Mitchell.
"He was good, he did (his job), being a superstar.
"It's going to take him a while, he's been out of football for a long time and there are guys who are four or five weeks in front of him.
"Each week he'll get better now."
The gutsy nature of the win led Bennett to rank the victory as one of the proudest of his decorated career that spans more than 1000 games across NRL, Test football and State of Origin.
"In my coaching career, it is in the grand final," Bennett said.
"To overcome what they overcome tonight, it was pretty special."
Souths had an 8-6 lead at halftime after Mitchell kicked a penalty and Junior Tatola cancelled out Sandon Smith's opener for the Roosters.
Walker didn't return in the second half and Ravalawa limped off soon after Billy Smith scored for the Roosters.
Injury-hit Souths were barely holding it together when Dom Young crossed on the Roosters' right wing in the 53rd minute to make it 14-8.
But even with Jack Wighton filling in as a winger for Souths, forwards Jai Arrow and Tallis Duncan sharing centre duties, the Roosters couldn't land a knockout blow.
"We created the opportunities and got enough to get in front, but we left some (points) out there," said Roosters coach Trent Robinson.
"We still should have finished it off at 14-8."
Mitchell was trying to conjure some magic in Walker's absence
He did so courtesy of the dropout that looked like a mis-hit when the first bounce landed closer to Souths' tryline.
But the ball trickled back towards and then over the 10m line.
Arrow was quickest to react and the Roosters' ill-discipline allowed Souths up the other end where Gray finished a Jayden Sullivan break.
Then the headline moment came with 10 minutes left as Tass touched down off a pinpoint pass that etched a new chapter in the storied career of Latrell Mitchell.
