Sam Walker was back in the Sydney Roosters side less than four weeks after suffering a syndesmosis injury, making his selection a significant gamble.
Coach Trent Robinson had Hugo Savala on the bench as cover, but the Roosters' dominance allowed him to use only three substitutes.
Savala came on with ten minutes remaining, giving Walker an early finish. The decision to bring Walker back paid off.
The Roosters pulled away after halftime, ending the Dolphins' season with a heavy defeat in Friday's preliminary final on the Dolphins' home ground.
Sydney now faces either the Penrith Panthers or Newcastle Knights in next week's grand final.
Inconsistency had troubled the Dolphins throughout the season, and their finals campaign exposed the problem again.
They needed a major comeback to beat the Warriors in Week 1, reflecting a reliance on brief scoring bursts that had often characterised their season.
Reaching the preliminary final showed the Dolphins were a strong side, but they will need more defensive resilience, particularly through the middle, to contend.
They must also reduce errors, which tended to accumulate in their poorer performances. The finals experience should benefit the team next year.