I would make the coop tall enough you can walk in it. In the long run, you'll be much happier because all coops need maintenance from time to time and it's much easier to walk in and do it than reach in. The standard for coops is 4 square foot for the coop, and 10 square feet for the run per chicken if they are going to be confined there. If your birds will be free ranging you won't need as much space. For 16 birds you would need 64 square feet or in other words about an 8' X 8' coop. There's a lot of factors that enter in here. How much outdoor space they have. How much roost space you have, etc etc. And this is just a standard to start with. The size of your birds makes some difference as well.
The roof line etc doesn't make much difference. Just be sure to plan for plenty of ventilation. I like to make a "screen door" with hardware cloth for summer and a wooden door for winter so I can allow more or less air in depending on the season. Things like a screen door can be added later though if you don't want to take on too much at once. Windows and or vents are pretty important. It's also wise to set the coop so the north is protected against winter winds. I like windows on the south also so you can get some solar gain from the sun in winter and be able to ventilate in the summer.