However the dual international said returning to the NRL was not his preferred option, but he did not want to go back on a handshake agreement with Roosters chairman Nick Politis three years ago.
Williams said he had grown to love rugby union after a successful stint that saw him with a Super Rugby title with the Chiefs, and the World Cup, an expected the change back to league to be tough.
He is currently suffering from a torn pectoral, which will take two to four months to heal, but hopes to be fit for round one of the NRL season in March.
He expects criticism about his return after he walked out on the Bulldogs in 2008 to join French rugby club Toloun.
Williams said he was looking forward to getting stuck in.
“The boys are a great bunch of blokes, a bit like the Chiefs, they’re real young,” he told APNZ.
“I’m looking forward to getting back out there in a game I grew up playing and put my best foot forward.
“It was pretty tough (to come back). It’s tough, but me and Nick are good friends, good mates.
“He tried to get me when I was an 18-year-old.
“When I made that (handshake) agreement with him I knew it would always be the case … glass half full.”
He confirmed he would not box during the season, but would not say whether he would be available for the Kiwis at the end of next season.