If you know they do, great. If they don't, a problem might just arise. Very often this type of help leaves the homeowner without recourse if the work or material is faulty. If these questions are moot, use these people as they will probably save you money. Handymen have a very important role to play in roofing.
Many handymen are retired contractors working alone.
This type of help is very useful for smaller jobs and projects. By owning a business, they afford the minimum in recourse, their business license. Usually lack of overhead costs make handymen less expensive than a quality roofing contractor. Often, the size of the job is the major consideration in selecting a person who cannot legally write binding contracts. Like mentioned though, not all persons in this category are without contractors licenses.