Judging by the look I assume you're going for, I'd go for a green looking roof possibly? it might be a bit of a cliche to match up the flooring with the roof but it does, in all honestly, correspond and look rather majestic.
There's a couple of different roof styles you'd want to dive into, like over-hanging, fitted or messy. These are the 3 types of roof styles I use and, yes, named. (Should note that these are probably real style types and in no way did I create them if so.)
Over-hanging is pretty self explanatory by it's name, it's a roof that goes either 1 or 2 blocks over the outline of the walls.
Fitted is the opposite of Over-hanging, with it's name being a big clue, Fitted is a roof style that I believe to be, well, fitted to the outline of the walls.
And messy, is just as it sounds. Get creative, do something no-one has ever done before. Discard the outline and make something completely new, but most of all, make something you think looks good. Because at the end of the day, as long as you like it, then that's all that counts.