First, I'd have to ask, why? Just for looks? I think my paints and TB look GREAT with roached manes, but I love the wild, "just climbed off the mountain" look.
You need to ask yourself about your horse's climate and contact with flies. The main reason for the mane (no pun intended... LOL) is firstly their heater and A/C, and secondly, protection from pests. If your horse is in a really hot/cold climate they must have good protection from the elements. If the flies situation is bad, you might reconsider.
Put up a picture of him on the critiques section and ask there! You might get some different answers!