I prefer to roll into a invert ,if your plane rolls slowly help it along with the rudder to get it inverted. Trust me it will roll faster using the rudder and Ailerons together. As other have said point nose up and then use both rudder stick and Aileron together to roll which ever way is comfortable for you and be ready to us some down stick to maintain altitude.

Practice doing a lot of quick rolls with both stick until you get use to it, THEN JUST STOP IT HALF WAY AROUND when you fell ready of course.