Roan is a colour pattern caused by white hairs mixing with coloured hairs. On a true roan horse the white hairs DO NOT mix in the legs and head of the horse, these areas remain the original colour. 
The Roan pattern is caused by a dominant gene, so a horse must have a Roan parent to be a Roan.

• Roan is not progressive - a horse will be born Roan (although it may not be visible until the foal is a few months old) and will be Roan until it dies.
• One trait found with the Roaning patterns is for the points on the front legs to come to a sharp point above the knee.
• When a Roan horse is injured the hair over the scars usually grows back the base colour instead of white as seen with most other colours.
• Roans will change from season to season, but no matter how light the body gets, the head, legs, mane & tail will always stay coloured.

• Some Roans get darker with age, a Grey will always get lighter.

• Roans CAN have primitive markings - we have an excellent example of a roan with the brindle pattern.

One belief is that roan in the homozygous form is lethal (lethal to the foal if it gets a roan gene from each parent), and this type of lethal foal aborts early in the pregnancy. Scientific evidence is yet to prove this theory either way.

>> Roan Examples