"It was a bit of a nightmare," said Roosters skipper Braith Anasta, who was celebrating his 250th game.
"I just couldn't believe it had happened. It was just total shock.
"I will never forget that one, it's a 250th to remember."
Souths coach Michael Maguire admitted he reminded his players of the round one result in the dying stages.
"We learnt the hard way in round one," he said.
"The message went out from our trainers, we've had it done to ourselves so lets go out and play a bit of footy."
For Reynolds, the finish added to a rookie resume of match-winning plays.
"You definitely dream of it as a kid," Reynolds said.
"You always want to score the winning try and you watch your heroes when you're a little boy and when they score a try you want to be like them."
The Roosters were seemingly gone when Mitchell Pearce scored with five minutes to go to give the Roosters a 22-12 lead, and even when Merritt scored his second of the night with two minutes to go, victory seemed impossible for the Rabbitohs.
But this is a Bunnies side on a mission, now two points out of top spot and with a friendly run into the finals.
The Roosters had shown tremendous courage to recover from a 12-4 halftime deficit to score 18 straight points in the second period - and even an unbelievable no-try ruling against BJ Leilua by video referee Russell Smith looked like it was going to matter.
Leilua scored six minutes later to give the Roosters the lead before Pearce extended it beyond a converted try, but it was all to no avail as the Rabbitohs came home late.
The only down side for the Rabbitohs was Luke being put on report for a dangerous throw on Shaun Kenny-Dowall which could land him in some trouble with the match review committee.
- AAP