In order to design and construct roofs to be vented or unvented in any hygrothermal zone is the main idea of the 
following document. It is a research report document related to the roof design that was written by Joseph Letiburek in 2004.
What you will find are sections such roof design in hot and cold climates, the main strategy utilized when designing roofs, Vented Roof Assembly, Unvented Roof Design and Assembly, the use of Rigid Insulation, Air Impermeable Spray Foam Insulation, and Unvented Flat Roof Assembly. All sections are described with clear explanations and illustration picture to help you understand.
Get and download How to Design and Construct Roofs in Hygrothermal Zone in a pdf filetype (source: buildingscience.com). Or you might interest in another diy home design article in this blog
