The versatile 28-year-old will join the Eels next year after he rejected an offer from Newcastle Knights.
Ferguson has scored 10 tries in 16 NRL games for the Roosters this season and put his outstanding form down to improving his off-field discipline.
"I had a conversation with him about how important it is for us that we want the right people and good people at our club," Eels coach Brad Arthur told NRL.com.
"We're going through a period where we want to make sure that everything we do on the field and off the field is professional and meets the standards and expectations required by our club.
"He's fully aware of his responsibilities and accountability to his team-mates and the club and he wants to be one of the players that can lead that."
Arthur added: "We'll have to wait and see [which position Ferguson plays], but he's going to help us out of the backfield.
"He can play centre, he can play wing. He's a big body and he's probably the form outside back in the comp at the moment.
"He's a quality finisher and is good at getting sets started out of the backfield."