Her legs make me think gray also. I've seen roans with tails affected by the roaning, so I wouldn't go by that alone. I wish I had taken a picture of the one I have in mind; his tail was awesome and quite unique.
Roan doesn't affect the face. The roaning may creep up onto the cheeks, but it will not be on the face itself. Roan also does not make any marks on the lower legs, the solid portion typically ends in an inverted V. Gray, however, will turn everything.
In the summer her face is the same grey as her body. Because her mane, tail, and knees are blackish brown; I was thinking a roan? This is a hard one! Posted via Mobile Device
Oh if her face is whitened too then its probably a grey, what age is she? How long have you had her?
The mane/tail of a greying horse usually stays its based color for the early stage and sometimes darkens with greying before lightening, Also, many grey horses keep their legs dark for the majority of their lives,
Examples I have found of horses whom are grey and have dark mane and/or knees but are grey not roan:
So going by her knees and mane/tail are not to reliable.