It's in the drugstore. It's either in water or glycerine sold as a topical product. I say leave it out. I doubt that either form would survive baking. Icing is usually not cooked, so it might add fragrance there, but in baking it would disappear. Walgreen's carries it.
Vitamin Cottage and other health food stores also carry rosewater. I agree with Andidandi that it is way too fragile a fragrance to use for cooking. I often spritz it on pillows but it fades in less than a minute.