Envisioneer offers two quick methods to put a roof on a house. If the shape of the roof matches the exterior wall footprint then use Roof by Perimeter which automatically matches the shape of the roof to the house. If the roof deviates from the outline of the exterior walls than use Roof by Picking Points and this will allow you to pick points to indicate where each corner of the roof lies. Regardless of which tool you use initially for the roof, the walls and the roof will become a cohesive unit and the roof will update if the walls move. Envisioneer offers many editing tools that allow you to create a complex roof system.