The striker has been sidelined since Reading's 1-0 defeat to Southampton on December 8th and continues to make slow progress in his recovery.
Pavel Pogrebnyak's absence due to a three-game ban has further shortened the club's attacking options, but Roberts admits he cannot be rushed back into action.
"It's going slowly with the hip and there is no real time line on it," he told the Reading Post.
"I'll keep working on the training ground to get it right.
"It's not cut and dry, that's the nature of the injury. We're working as hard as we can to try and get it right.
"We've exhausted everything we can to try and make it right. If there is an opportunity of us managing it, then we certainly will do."
Reading have slipped to second from bottom in the Premier League, but Roberts insists they must maintain an attacking approach as they attempt to pull clear of trouble.
"There are still big games to go and it doesn't change what we need to do," he said.
"We need to be positive. We attack every game with a positive attitude and there is no other way."