Hmmm . . . Nope,
Winter Rose isn't a re-telling of "Snow-White and Rose-Red." There are a couple of similarities though--like the two sisters, one who prefers to stay home, and the other who likes to be outside in the forest.
There are also similarities to "The Snow Queen," I think, but I can't really name them.
Whether or not it's a re-telling of a classic fairytale, I'd still recommend
Winter Rose, just for the imagery (great discription in that book, there is) and for McKillip's rather neat writing style. Not to mention, the story itself is an intriguing fantasy/mystery.