"It was a great game. It ebbed and flowed and it looked like it was going to finish goalless but with the chances we missed that would have been unfair," said Cotterill.
"We could have been 3-0 up after 20 minutes so although we left it late, we deserved all three points. Credit to Rotherham though because they gave our central midfielders a really hard time.
"One-nil victories win you leagues and I'm extremely pleased we kept another clean sheet, which is our seventh in eight games.
"Since I've arrived I've been impressed with the quality from the players I inherited. They've been first class and I can't credit them enough. I want to keep pushing them to make sure they get their rewards."