The attacking midfielder spent the second half of last season at the Riverside, scoring once in nine appearances in all competitions after arriving in January, and also making three assists.
Warnock thinks he will notice a difference in a squad he only left in mid-July.
“If he gets his head up and his confidence, I think he’s coming into a different team to the one he played in last season,” he said. “He’ll get more balls and opportunities in areas where he’s dangerous.”
The Boro manager believes 23-year-old Roberts will add much-needed creativity and allow him to play Marcus Tavernier in his best position.
The latter was impressive as a right wing-back in the club’s recent 2-1 win over Barnsley, helping to create both goals with his shots, Jonathan Howson volleying in after his free-kick hit the crossbar and Chuba Akpom putting in the rebound after Brad Collins saved a long-range effort.
“It just gives us something different,” commented Warnock. “At the moment I’m asking Tav to play in the hole and I think he’s happier when he’s got a line down the side of him.
“(Roberts) might not start every game but we’ve got so many games coming up.”
Roberts has two more years on his Manchester City contract, but has not played for them for five years.
He has also had loans at Celtic, Girona and Norwich City.
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