Roofing is one of the few skilled professions where being a licensed contractor is not required if you do it on your own home here in Salem Oregon. Hiring a licensed contractor is definitely encouraged, however a home owner with a little DIY initiative can tackle the job on their own with no distractions (like code enforcement inspections) from the city building department.
A roof shingle system is one of the few things on a home that will wear out. Unlike siding that can be painted and painted and preserved for eons, there is nothing to do about your roof shingles wearing out. There are things to do to extend the roof’s life. Adding ventilation, keeping debris off, treating moss and having a very steep roof will all prolong the life of the roof however even the best ventilated, cleanest, and steepest roof will generally only increase the life of the shingles by 20 years max.
Enter the creative home owner:
One way or another most homeowners will face a roof replacement at some time. Just like most trades you do not have to be a Harvard graduate to install a roofing system. The steps are, overall, very straight forward and logical. The problems most unskilled craftsmen face will be at tricky transitional zones: flashings, valleys, roof-to-wall and the dreaded skylight. It must be a testosterone thing but from what I have seen as a home inspector if problems are encountered they are handled one of two ways: Gallons of roofing tar, or scab-it-in and forget-about-it.
I guess maybe I have seen some roofs that have been replaced by home owners who knew enough to know that they needed some advice. That is what the internet is for as far as I am concerned. Those roofs maybe just flew under my radar mostly because they were done properly. So thank you very much to those homeowners who stopped and asked.