What is the roof shape?

Since the buildings appeared, roofs have appeared. In general, any building is always a crown — a roof. How to determine what it should be? The shape of the building may be partially determined. The truth is more dependent on the functional purpose, aesthetic need or the desire to save. In all cases, the choice of form should not be saved on the quality of the coating, as a result, any roof is the protection of the house from atmospheric phenomena, and saves heat, thereby bringing comfort.