Sydney Roosters are through to their first NRL grand final in seven years after Mark Nawaqanitawase genius and a miracle Sam Walker injury comeback inspired a 36-20 demolition of the Dolphins.

The Roosters, boosted by a Nawaqanitawase intercept try against the run of play, shot out to a 16-0 lead inside 27 minutes in front of a sold-out preliminary final crowd of 52,286 at Suncorp Stadium on Friday night.

Their defensive grit on the tryline, a feature of their finals campaign, limited the damage from a mini-Dolphins comeback, but two-try hero Nawaqanitawase has a box of unlimited magic tricks that he unfurled with a wow factor rarely seen on a rugby league field.

The Roosters lost bench rake Connor Watson to a category-one HIA, upgraded by the independent doctor, in the first half and the St George Illawarra-bound utility is set to miss the grand final.

Roosters coach Trent Robinson said “watch this space” when asked if Watson, who was undergoing further tests post-game, would seek an exemption to feature next Sunday.

Victor Radley’s participation is also in doubt after he was reported for a hip-drop tackle on Herbie Farnworth, although Robinson felt he didn’t have a case to answer given the Dolphin’s legs were already grounded.

Roosters coach Trent Robinson chats with Connor Watson after the match. Photo: AAP

The Dolphins had won eight straight games to reach their first preliminary final, a wonderful achievement, but on this occasion it was the Roosters’ big-game players who stood tallest.

Walker returned in a record-equalling 27 days from a syndesmosis injury to orchestrate the backline in a masterclass to set up a decider against either Penrith or Newcastle.

He finished with his leg strapped in ice, but Robinson declared his playmaker “fine”.

After his stunning return from injury, Sam Walker finished the game with his leg strapped. Photo: AAP

Robinson will be angling for his fourth premiership win in as many attempts.

An error or a moment of magic was needed to turn an early set-for-set stalemate, and the paranormal Nawaqanitawase provided it in the 18th minute.

The rugby-bound revelation’s pivotal moment was pure instinct and skill, backed with supreme confidence.

Dolphins centre Farnworth hesitated with his pass for what would have been a Dolphins try had it hit the mark. The man known as “Marky Mark” swooped, raced 90m and the Roosters never looked back.

“It’s incredible to watch him play. It’s pretty rare, such a care-free, instinctive player,” Robinson said of his Japanese rugby-bound winger.

“We were physical getting off the line, intent post-contact and in the carry.

“It started there and … that allowed some freedom for some individuals.”

Dolphins bench impact man Kurt Donoghoe dropped the ball when he came on, then missed a tackle for a rampant Radley to score.

Walker’s sublime lob for jumping Daniel Tupou had been well rehearsed and was perfectly executed.

Dolphins winger Jamayne Isaako scored tries either side of halftime, but Nawaqanitawase collected a kick and flicked it back for Robert Toia to crash over.

When Nawaqanitawase bulldozed over for his second and Walker sliced through, it was all over for the hosts.

“We started really well and did all but score on that first opportunity,” Dolphins coach Kristian Woolf said.

“It was a great take from Mark … if he doesn’t take that, we score (and) we didn’t quite recover.”