In some states, it is relatively easy to get a contractor's license. File the paperwork, pay the licensing fee, and you are done. In other states, it is more complicated than that. The following shows how complicated things can get in the states that do not just hand you a license for filing the right paperwork and paying your fee.
Taking a Class
Some states, like Florida, require you to take a full six-month to two-year course on roofing. That is somewhat understandable, given the fact that homes in Florida have to be hurricane-proof. However, in some other states that make the same requirement, it seems a little overkill, especially if you have experience with roofing and you know how to install and apply various roofing materials. Yet, the class is more about state and local building codes, and less about how to manage a nail gun and applying shingles. In that light, it may be valuable to you as a contractor to take a class in order to get the license you need to be a full-fledged roofer.
Stranger still are roofing exams. Some roofing exams are all onsite quiz and physical testing (e.g., show how you apply a metal roof, show how you apply underlayment, etc.). Other exams are all classroom tests, asking multiple questions and providing multiple answers regarding mathematics, weight- and load-bearing calculations, application questions, etc.. These paper-only exams test the would-be roofer's (that is you!) knowledge and expertise. The exams are pretty extensive, and you have to score very high on them before the state will grant you your license. Generally, you will know in a month or less if you have passed, and the paperwork you need to apply for a license (or the license itself) will be in the envelope with your test results.
Just like college prep courses, there are roofing exam prep courses as well. Regardless of how well you think you know your business, it is a good idea to take the prep course. You may be surprised at how much stuff is covered and asked on the exam that you did not know or did not know was going to be on the exam.
Three Years Working as an Apprentice
Still, some other states require that you spend one to three years working as an apprentice under the tutelage of a licensed contractor. This is often in place of a classroom setting. At the end of your apprenticeship, the licensed contractor gives you the documents you need to apply for your own license. Check with your state and local licensing boards to see what you need to do to get your license.