Ah I missed those commans
I've never used Slick2D which should not be a problem here at all. You just match the way it rotates.
Does it work with 0 degrees? Did you try outputting the values? If so, how are they acting? If I'm debugging it, I would start from there to find out what is not acting properly.
I can't tell much from the given piece of code. If you can show me a code that I can actually run and test, I could help more.
You do understand the idea, right?