but the if you snare in the channeled part, does it stop the teleport and keep him there with his crows, or does it still teleport him, or does it just completely break?
It still teleports him.
Silence, stun, knockback, or knockup during his channel cancels the ability.
So here's one of my smurf account's match history:

That quadra right there would have been a penta but the last one was rammus.
I ulti'd him while he was rolling away but he survived with 10 hp left.
That pissed me off a little, but whatever.
That TF game i was trolling, honestly. I don't even know how we won.