Roan comes in any parti color from :
The AKC defines roan as "FREQUENTLY A BLUE-GRAY OR IRON-GRAY, THIS COLOR IS THE FINE MIXING OF COLORED HAIRS WITH WHITE HAIRS. FOR EXAMPLE, A BLUE ROAN IS A COAT COMPRISED OF BLACK AND WHITE HAIRS"
Roan is actually a pattern and not really a color. Roan is visually a parti color and thus in that 'class' vs a solid which can appear to be solid due to the filling in of black (darker) hairs on the white (parti pattern) areas of the American Cocker Spaniel.
Primarily you need to have one of the parents be a Roan in order for your puppy to be one.
So knowing what the parents looked like as puppies is helpful because Roans can fill in and look like either a mismark or a solid depending on how 'heavy' the roan pattern is in that adult.
Unfortunately 'color'/pattern bias is prevalent in the American Cocker Spaniel.
Before the AKC had merle and the Z list (to identify merles) people were advised to register their merles as whatever color/pattern that they most closely resembled. So many blue merles were then registered as blue roans. There is disagreement as to whether the merle breeders and owners were being dishonest and such but it's my opinion that those that continue to register without the merle z listing are now being dishonest where as before they had the benefit of the doubt as there was no way to list merle.
I will be working to transfer some photos from my 1st Roan Litter to show you the progression of roan in the puppy as it grows. In the mean time there is an article using those photos and talking about my experience in September 2016's Edition of Cockered Magazine.