A ventilated roof will also help keep rotting and warping of siding as well as mildew, drywall damage, and peeling paint both inside and out. It also keeps moisture from being trapped in structural wood, insulation, and shingles.
When the roof is properly ventilated, it allows air to flow naturally into the attic, and back out again. It also prevents excess heat and moisture to accumulate in the attic, which would lead to the need for a new roof earlier than planned if contained in the attic for extended periods of time.
Having a properly ventilated roof allows your home to breathe. When the excessive temperatures are released from the home instead of into the living areas of your home, it keeps the temperature of the home at a stable level throughout the house. This reduces the need for your heating/cooling system to be used, in turn reducing the energy your home needs to function.