Definitions of The Roan Gene

Roan Pattern. The loci is R, roan. The nature of the coat pattern and the progressive development of dark hair in a light area is unclear and still in debate. Roan is  defined as "having the base color (as red, black, or brown) muted and lightened by a mixture of white hairs." In American Cockers, it is colored hairs (black, brown, red) within a white base.Roan (R) appears to be dominant to (rr) non-roan, i.e. open marks. Roan can carry for open marks, but open marks cannot carry for roan. So in other words,  A open marked parti that isn't a roan, cannot carry for roan. Therefore you have to have a roan to produce a roan. Two non-roans (even if one or both have a roan parent) will not produce roan. 

The roan gene in dogs acts as a simple dominant gene. The action of the gene results in a mingling of colored and white hairs. To be roan a dog must have white areas; a solid colored dog can not be roan. However, mismarked solids can and do show the roan pattern in their white, so some solids may carry the roan gene, but not manifest it due to them not having white.
Black and white roans are referred to as "blue roans" (spaniels) or "blue belton" (English Setters). Red/buff and white roans are referred to as "red roans" "orange roans" or "lemon  roans" or orange. Brown and white are referred to as "liver roans", "chocolate roans" or "brown roans".

 

• Roan is dominant over open marks. 

Roan can carry for open marks, but open marks cannot carry for roan

Ticking is by some considered to be a form of roaning, by others to be a different gene. Those who feel it's a different gene consider it recessive to roan but dominant over open marks. 

There are color gene modifiers that set theories askew.

Example: Dark roan is dominant over light roan therefore two light roans cannot produce dark. However, we all know lighter roans producing darker roans. What is in action here are modifiers that affect the extension of color. Similar to why some tan marked dogs have a lot of tan, others just have small spots. Their pads of their feet will be black and their nose area will start getting this smudgy look within days of birth. The degree of how much the roan gene affects a dog varies. 

The standard states:

• Parti-Color Variety-Two or more solid, well broken colors, one of which must be white; black and white, red and white (the red may range from lightest cream to darkest red), brown and white, and roans, to include any such color combination with tan points. It is preferable that the tan markings be located in the same pattern as for the tan points in the Black and ASCOB varieties.

  Roans are classified as parti-colors and may be of any of the usual roaning patterns. Primary color which is ninety percent (90%) or more shall disqualify.

  Tan Points-The color of the tan may be from the lightest cream to the darkest red and is restricted to ten percent (10%) or less of the color of the specimen; tan markings in excess of that amount shall disqualify. In the case of tan points in the Black or ASCOB variety, the markings shall be located as follows: 
  

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    1. A clear tan spot over each eye;

    2. On the sides of the muzzle and on the cheeks

    3. On the underside of the ears;

    4. On all feet and/or legs;

    5. Under the tail;

    6. On the chest, optional; presence or absence shall not be penalized.

  • Tan markings which are not readily visible or which amount only to traces, shall be penalized. Tan on the muzzle which extends upward, over and joins shall also be penalized. The absence of tan markings in the Black or ASCOB variety in any of the specified locations in any otherwise tan-pointed dog shall disqualify. 

    This is from the AKC Judges Newsletter to help clarify the roan color and in no way reflects any change to the approved 1992 standard as written above.
    
    Roans are classified as Parti-Colors and can be any of the usual roaning pattern. They have colored hair intermixed with white hair, but the colored hair is not white tipped. They may be totally roan with or without head markings, with or without body markings or any such dog with tan points. Primary color which is ninety percent (90%) or more shall disqualify.