So this new Gen 6 mechanic is that when you switch out a Pokemon who is asleep, the sleep timer doesn't reset when they switch back in, but does that get affected by Whirlwind/Roar?
Or even Dragon Tail.
the user of rest will always sleep for two turns, no mater if it switch or get roared.
source: I tested it out
unforantely, I forgot to save the battle replay (facepalms myself) but I'm sure someone can back my claims :)
hope I helped :-)