Roof Design by Joseph Lstiburek at Building Science

[MountainDon]

Good info covering different climate zones. This is not so much as how to build the structure, but how to design a vented or unvented roof and different designs for insulation type and placement.

http://www.buildingscience.com/documents/reports/rr-0404-roof-design

Once the page is opened the document can be saved as a PDF file.

[MountainDon]

A companion article...

BSD-102: Understanding Attic Ventilation

Again both vented and unvented considerations

Understanding Attic Ventilation

[MountainDon]

And another...

BSD-149: Unvented Roof Assemblies for All Climates

http://www.buildingscience.com/documents/digests/bsd-149-unvented-roof-assemblies-for-all-climates/?searchterm=roof%20design