I honestly doubt it would kill the rooster, as my chickens have hit the electric fence a time or two without issue. The biggest issue as I see it is the weight of the unit, and how to attach it. We have used ours on our yellow lab 4 times (chasing a car, deer, and heading to the road twice), and it has a vibrate feature as well. Now all we have to do is hit the "buzz", and he stops, and there is no pain. If you have one with dialed up power, a vibrate option, AND you figure out how to attach it, try the vibrate/buzz first.
Tried my dog's collar, just so I know what it felt like. Even on 16, the electric fence stung more, and we have a 0.2 Joule fence.
Sorry for the trouncing folks have been giving you.