(Also see Energy Codes.)
2. General: A best practices "RICOWI Roof Guide" is available on the website of the Insurance Institute for Business & Home Safety. ("RICOWI" stands for the Roofing Industry Committee on Weather Issues). This is an excellent resource with particularly good explanations of building code requirements as they pertain to roofing.
3. General: Copyright law regarding building codes: This: Veeck v. Southern Bldg. Code Congress Int'l, Inc., yet also this: Federal Court Basically Says It's Okay To Copyright Parts Of Our Laws. We don't know what to make of it all. (And now this: Can the Law be Copyrighted?.)
4. General: The Building Codes and Standards page at the website of the National Roofing Contractors Association is a good place for up-to-date information about building codes and how they affect roofing.
5. General: An excellent one-page explanation of the roofing section of the 2012 International Building Code. From the November 2012 issue of Professional Roofing magazine and archived at the website of the National Roofing Contractors Association.
6. General: To view actual US building codes, plumbing codes, fire codes, etc., (check the website of your local building inspector's office to find out which code is currently in effect in your area) see UpCodes. For example, see here for a look at the roofing section of the 2015 International Building Code. See here for a look at the roofing section of the 2015 International Residential Code.