I do a LOT of long climbs in the mountains and I don't sit up with my hand on the tops. If I want to apply more torque for a brief steeper section, I do the opposite, I lower my torso angle even more. I also ride with my hands on the hoods and my torso angle is relatively low, with a 12cm drop from the saddle to the bars.
I think the term "rolling the hips forward" is unclear. If viewed from the right side, a CW rotation at the hip might flatten the back a bit.
I also think that most people have a natural position for the hips at any given torso angle and there's not much alteration that can be made without discomfort.