Flat roofs are often installed on pitched decks so that the majority of insulation is of continuous thickness. Crickets are created around the perimeter by tapering the insulation layer for drainage and wrapping the membrane over the wall. Revit however does not allow for modifying sub-elements on pitched roofs.
This sticks us with the task of modifying the entire roof from flat for both crickets and the primary pitch. What's wrong with that?

That's what's wrong with that. Because parts of the roof end up below the base level NONE of the layers can be variable, so the rigid insulation can't be shown tapering properly. We're left with an air space under the cricket that has to be filled in graphically. Joins with walls also cause errors that can't be fixed by changing the join order. Even if you try to build the roof out of individual segments you can't taper a layer from both sides.
We need the ability to establish a base slope for the whole roof with the option to thicken portions where needed.