I had the same concern about Petey, our roan piggy (may he rest in peace).
So I asked about it on GuineaLynx, and they told me that being a roan pig, in and of itself, is not a problem. It's only if they breed with another roan (or dalmation) pig that can be the cause of lethals being born.
Since we do not breed in any way, shape, or form; that put our minds at ease that we didn't have to worry about Petey having health issues due to being a roan.
Thanks for this. My pig is roan (although the light hair has been shedding out lately) and I was a little anxious until you posted this.