Playing Geb these days I've discovered a bug that I'm not sure if was already there or was created in the last patches. The problem is you can't hit minions twice with Roll Out once you have swapped phases from normal speed to double speed. If you hit them at normal speed they will become damage immune when you try to hit them at 2x speed and I am sure this is not intentional since there is no reason you shouldn't be able to do so and it's wasting clearing potential.