The Welshman had scored only four goals in 56 games before making a summer move to play under Saunders, who had worked with Cotterill during his time as the assistant Wales manager.
The 24-year-old is now back among the goals, finding the net seven times so far this term, and after frustrating spells at Swansea, Portsmouth, and Barnsley, Cotterill is enjoying life at high-flying Rovers.
He said: "It's nice to have a manager who believes in me and to be playing week in and week out, because it's probably the first time in my career that I've had that.
"The manager was a striker when he played and he scored a lot of goals and he's helped me a lot since I've been here.
Cotterill added: "It's not surprised me where we are (in the table), I thought we'd be there or thereabouts."