Actually, on turns I did not roost... It did more than the amount of damage you said it would minimum, probably due to my non maxxed out Sdef. When dragonite was first hit with Ice beam upon coming out, and every time he snuck in a Dragon Dance, it hit for approximately 240 damage. However, since 240 + 120 only equals 360 as opposed to 385, and I had leftovers, it was not only possible.... But fairly easy to turn Swampert into setup bait with Dragonite.