A gazebo is a free-standing, open shelter, usually placed some distance from the house for privacy. Often raised a step or two above ground level, it is sometimes surrounded by a railing and built-in bench seating. Sometimes it takes the form of a raised, covered patio that is ideal for summer dining. Mosquito screening provides protection from mosquitoes and other biting insects.
Your choice of roofing will determine how you use your gazebo. Some structures are constructed with open lattice roofs over which vines can grow. The openness allows some penetration of sunlight and maximum ventilation. A closed, watertight roof, covered in shingles or metal panels, provides protection from rain and can be enjoyed during inclement weather.
Lap siding -- also called bevel siding or clapboard siding -- is designed to provide protection from the elements when it is applied as a vertical siding material. Watertight because of their overlapping application and their bevel which sheds water away from the house, it does not make a good roofing material. Sometimes boards are used to cover a gazebo that shed water, yet still allow ventilation through the roof. This louvered installation, in fact, can sometimes look like lap siding.
The sky is the limit. Anything you can use to roof a house, you can also use to roof a gazebo. Consider how you plan to use your gazebo. If cool breezes in a hot climate are of paramount concern, then open roofing may be the choice for you. If you need protection from the rain or biting insects, you'll require a watertight roof. Gazebo design is often complementary to house design. Roofing can play a key part in achieving a unified architectural look.