Prednisolone definately causes changes in the bodies usual hormone levels including those that cause acne, I feel for you as i know that steroid induced acne tends to be quite severe. My thoughts would be that the hormonla treatment would be the way to go- roacutane has some significant side effects and does not really do anything to address the underlying problem. There is no reason you could not try the vitamin supplements too but i would let your Dr know just to make sure they are not going to interact with any of your other meds

Steroids are very useful drugs and do a lot of good but unfotunately they have a lot of sideeffects that can be distressng long term. Weight gain, loss of bone density etc and the classic "moonface" and buffalo hump are some of them but unfortunately many of us have no choice but to use these drugs- i guess its a case of weighing up the pros and the cons
good luck