Angus Crichton will join the NSW Waratahs in 2027, pursuing a place in Australia's side for next year's home Rugby World Cup.
The 30-year-old lifted the NRL premiership trophy with the Roosters on Sunday, winning his second title with the club before beginning a new sporting chapter.
Crichton played union at The Scots College and represented Australian Schoolboys before winning the 2022 Rugby League World Cup with the Kangaroos.
His mother, Pip, celebrated with him in the Roosters sheds and told AAP she believes he can achieve his Wallabies ambition.
"When he was seven he had a sign in his bedroom that said, 'I want to be a Wallaby'. He crossed it out and then wrote 'I am going to be a Wallaby'," Pip told AAP.
"He always had that drive and that fire."
Raised in Young, NSW, Crichton grew up supporting the Roosters and also won the premiership with them in 2019.
Pip called his latest victory "such a fairytale ending" and said the club's coaching and friendships helped shape him.
Crichton told AAP, "I've loved my time here at the Roosters, a special time in my life and I will have these memories forever."
He and Pip hope to return to Accor Stadium for the Rugby World Cup final on November 13 next year.
"That's the plan," Angus said.