Here's another good example of ...well, it is what it is. http://www.co.yuba.ca.us/firesafe/protection-homeconstruction.htm "A good example of a noncombustible material is metal roofing and siding. Metal is non-combustible, but an excellent conductor of heat. If the fire remains present long enough, the heat will be conducted through the metal and ignite the material behind it." [emphasis added] I.e. ,what I said re treated cedar roofing being capable of being Class A, and better than a poorly done metal roof, is not just factual, but very well known in the real world.
Well-constructed metal roofs obviously are also ok, if posters are not simply looking to mislead, as has occurred throughout the thread. The helpful point to readers, that like so many factual, helpful points that are trying to be shouted down, is that you can get pretty bomber construction from a wide range of materials, including cedar for your roof. Which can be Class A.
The continual attempts to yell over factual information well, are what they are.
According to the California Energy Commision though metal is fire retardant whereas this is what they say about treated Cedar:
So given the shortage of available material and the fact that (again according to the CEC) metal roofs are longer lasting and require much less maintenance to maintain there is nothing wrong with metal roofs. True given enough time the metal can conduct enough energy to spark the other side, but that doesn't mean it is common. Theoretically the Large Hadron Collider can destroy the universe, but the odds are so minute as to be insignificant given the potential benefits. I have no reason to believe Bob is lying when he said in 32 years of firefighting he didn't see any fire result from metal roofs conducting enough energy to spark a fire other side. However his evidence is anecdotal and take it as such. It's not empirical proof that metal roofs completely stop fires. But keep in mind you also haven't provided any proof that metal roofs lead to any statistically significant amount of fires to warrant the switch--you've only provided a quote showing it is theoretically possible--over to Cedar roofs.
Given the statements from the CEC I'd take a chance with the metal roof. It is harder to build and maintain a wood roof over a metal one, so I'll go with the one thats harder to mess up.