As a general rule of thumb, the observing the following periodic maintenance routine is wise:
Having a regular roof maintenance check-up ensures you avoid serious issues before they come with a loud bang.
Moreover, certain random instances which could happen anytime of the year require you have a roof inspection in order. Some of these are:
Any time a storm, big or small, passes through, there will be damage to the house including the roof. Immediately afterwards and provided the weather has calmed down, it's best to do roof inspection or call a professional.
A thorough inspection after any drastic weather changes should be able to pinpoint the damage done to your roofing system.
A house may look perfect inside and out but you won’t know what it has been through structurally. If you think getting a professional inspector is going overboard, you can always do a quick inspection with a thermal camera.