Typically, if your garage is heated, insulated, or you are planning on heating or insulating your garage, then you will need to properly ventilate it. An inspection can be done to see if you do or not. Things that will go along with new roof vents are possibly new soffit venting and chutes that leave an ample space for air to flow from the soffit to the roof. Ultimately, your city’s building codes have the final say on ventilation in your home or other structures.