The roof is pretty much just blocking at this point. It also has a bit of a "split level" thing going on. The outer part is flat, meant to allow patrols. The block of blue will be a sloping roof; however, it is elevated by a row of short windows that let light into the ballroom below. For a soldier walking on the flat roof, the windows would be right at his feet and only come up to his mid thigh or so. None of that will be at all obvious from the map itself, which makes me want to build a Sketchup file of the bones of the place.