The only negative thing that I've heard about Rogaine is that you have to keep using it or your hair will fall out again.

My mum has suffered with bald spots and has tried several things (sulfur, castor oil, megatek and others), the thing that has worked best for her is Jamaican black castor oil (I have a YouTube video with her progress pics showing the results she got from each product if you want to see how she got on Hair Loss and Regrowth: Recovering from Alopecia (with before and afer pics) - YouTube )

Good luck and I hope you find something that works for you, I know how devastating hair loss can be