Not all steroids cause hair-loss, that's where you're wrong. And let's be technical, even cholesterol is a steroid. You meant to say AAS.
As I'm guessing you already know, Nizoral is just your typical anti-dandruff shampoo with only mild (and inconslusive) anti-androgen properties.
That being said, yes. If I were you I'd stick to Nizoral for the moment unless you start suspecting an increase in hair loss, then add Proscar to your arsenal.
Personally, I'm not prone to MPB but I like the fact is has very impressive effects in reducing the risk for prostate cancer.