As soon as I saw that pic of HF I knew there would be some jizz over the collar roll.
This is a concept which is entirely lost on me. I just don't get it - what makes having a collar roll like that so attractive? I don't even own any button down shirts so its more out of curiosity than desire to emulate.
Here is my take on it. If you are going to wear a button down collar, the roll provides a certain aesthetic continuity to the shape of the tie knot, and the blade. Button down collars with no roll leave an unpleasant straight line cutting through what is otherwise a rounded knot, often obscuring it in the process. A standard spread collar, or at least a collar that lays under the jacket lapels leaves the knot with it's shape visible, and also provides a continuity of shape with the lapels, but a button down collar, by definition, cannot do this. Or, the ones that can do it are too widely spread and might as well not be button downs to begin with. In order to maintain proportions, some roll is desirable. The extremity of that roll, however, is up to the user.
Keep in mind that I have no basis for this theory other than my own brain and it is probably wrong. As always, remember that I dress horribly and no one should listen to me.