The answer to 'how to repair roof vent' is to first inspect the vent for any damage or wear. Look for cracks, holes, or loose fittings that could be causing leaks or air flow issues. Depending on the type of roof vent, you may be able to make simple repairs yourself, such as sealing cracks or replacing worn gaskets.
However, for more significant damage or if you're unsure about the repair process, it's best to call in a professional roofing contractor. They can properly assess the condition of the vent, make any necessary repairs, and ensure the vent is functioning correctly and won't cause any future problems.