I'm an old school roofer. I've been in the business now for over 35 years and a 2nd generation roofer. I've installed most types of roofing on most types of roofs. Have not yet installed thatch, but would like to try, and never got a chance to install coal tar pitch. I'm thankful for the latter.
I learned the basics from my father and older brothers. I learned the rest from books and research but I learned the most when removing old roofing installations that had outlasted the roofing material.
My philosophy is that, every roof I install will someday be seen by another roofer. Hopefully later than sooner.
When that happens, I want that roofer to say " Hey, this old guy knew what he was doing."
Me, up on a roof restoring a leaded copper roof finial.