However, there's a decent chance that's not what he is, genetically. Roans don't typically have salt-and-pepper manes. They don't typically have skunk tails and barring above the tail.
He also quite clearly has a few primitive markings: a hint of a dorsal stripe and tiger stripes on his legs.
Since he was born in the wild, there's no way of knowing (at least at this late and far removed date) who his parents were, and no way of including or excluding certain possibilities based on their color.
Is he rabicano? Is he minimally expressed sabino? Is he mealy? Who knows!
His color is one of the reasons I've always been fascinated by equine color genetics. I am by no means an expert but I usually consider myself to have a decent eye.
Lesli at Equine Tapestry really is an expert. She writes about color with detail and precision, and backs her findings up with extensive photographs. She's always got a new, interesting quirk to talk about. I love reading every word of her posts and I always come away thinking. Consider this a strong recommendation to follow her!