"I would like to say thank you to everyone that has stood by me through the last 16 months good, bad and ugly.
"Happy to be a chook. I will continue to work on myself as a person and repay the faith the Roosters have shown me."
Roosters chief executive Brian Canavan confirmed Ferguson's contract included a number of safeguards.
Ferguson had his contract torn up by the Canberra Raiders in August 2013 and, by the time he steps out for the Roosters next year, will have spent almost 18 months out of the game.
"There are stipulations and criteria that have been extracted so that we as a club and Fergo [Ferguson] keep on a path and we stick to it during the year, so that we don't let anything slip," Canavan said. "We'll meet and report with NRL welfare and education staff.
"It's about checking in on the criteria that we've set for him on a monthly basis and to make sure nothing gets overlooked."
Asked if he expected criticism for signing Ferguson, Canavan said: "Not really. I think the initial reaction was that way when there was talk Blake may join us. But we got a similar reaction when we contracted Sonny Bill [Williams], too, and that turned out all right."
Canavan said the NRL considered registering the contract only after Ferguson had undergone regular counselling. He also completed community work and former club captain Brad Fittler was used as a mentor. Ferguson had also placed himself on an alcohol ban.
Canavan said the club didn't feel it necessary to enforce their own additional booze ban. "We're not going to impose that on him because we find they don't work," Canavan said.
Ferguson underwent surgery to his foot in November and is likely to make his first appearance for the club in their February 7 trial match against Penrith or February 21 trial against Manly.
He won't play in next month's Auckland Nines.