The "The Beast Within" talent makes the hunter immune to all roots, snares, traps, and whatnot. It only lasts a few seconds, and has a 2 minute cooldown. Easy to tell when a hunter is under the effect of this spell because he turns bright red.
There are meta gems that give increased resistance to roots, snares, and stuns. "Enigmatic Skyfire Diamond" to give an example.
SURVIVAL offers "Surefooted", which gives up to 15% chance to resist "movement impairing effects"
A survival hunter has easily a 20% resistance, without even considering possible dodges, misses, or maybe even racial resistance to stuns. I think it could be enough to make somebody appear immune.
Sometimes there is more to a question than it initially seems. Of course we wouldn't know, because we spend more time trying to appear smart than actually addressing the problem or question.