The loan midfielder hadn’t played since October 15, but impressed at Newcastle United as a substitute last Saturday when he was handed a rare chance by the Millers.
Now Warne is ready to use him again in this weekend’s Championship derby against Barnsley at New York Stadium.
“I thought he was good,” the interim boss said. “In training, he had been the most exciting player. He has the confidence and know-how to get on the ball.
“He was really positive when he came on so he’s in my plans for Barnsley.”
Allan replaced Jon Taylor in the 75th minute of Rotherham’s 4-0 defeat at St James’ Park and, despite giving the ball away to set the Magpies on their way to their fourth goal, was a real attacking threat.
The Millers have been expecting Allan, who has made only five starts since being signed by previous manager Alan Stubbs, to leave during the January transfer window.
Parent club Celtic have shown no inclination to recall him from his season-long loan, so the 25-year-old has been looking to broker a temporary deal elsewhere.
However, his recent form in training and the fact Rotherham are low are numbers because of a flurry of departures and injuries have brought him in from the cold.
Warne, looking to recruit players before the close of the window on January 31, has called on Allan to tighten up defensively and improve his workrate.
“I told him afterwards that he did well, but he needs to know the other side of the game as well,” the former Millers player said.
“I am not criticising him for that. He has had a different upbringing to what I have had. But he needs to learn the other side.”
Meanwhile, the FA say they don’t comment on individual cases amid reports they may be investigating the role Millers striker Dexter Blackstock is alleged to have played in Henri Lansbury’s move from Nottingham Forest to Aston Villa.
Blackstock is said to have acted as an agent to his one-time Forest teammate, which would be against FA regulations.