Keep it simple stupid.
Drawing a floor or a roof on a different plane.
Intricate roofs have many parts that incorporate several of the basic roof designs such as a gable roof sitting atop a gambrel or variations of the gable valley roof design using one or a variety of different types of roof trusses also see our very detailed diagrams showing the different parts of a roof truss.
Also different architectural styles will use the same type of roof.
The plan is typically cut at a height of about 4 feet but the architect drawing the plan may cut it at a different height.
In the two examples shown below the wall plans are identical apart from the parapet wall in roof b yet the two roof shapes are quite different as indicated by the roof lines on the plan drawings.
For each offset angle or change in plate.
This means that you have an imaginary plane cutting through the building at an elevation of 4 feet above the floor.