When reviewing the results of a home inspection, I usually discuss with my clients the importance of yearly roof maintenance. It's better to proactively identify and deal with potential problems before they become widespread. In many cases, if a problem is identified early and properly repaired, the extent and cost of the repairs will be significantly less than if problems were unattended.
I recommend that homeowners have their roofing systems inspected every year or two depending on the conditions around the home. You can perform a preventative maintenance inspection on you own roof if you have the knowledge, ability, and follow proper safety procedures. If you aren't comfortably doing your own preventative maintenance inspection or being on the roof, hire a professional roofing contractor.
A typical preventative maintenance roofing inspection usually consists of a thorough visual inspection of the roofing system and intersecting wall surfaces, as well as all protrusions, (vents, soil stack, chimney, skylight, etc.) and gutters. It's a good idea to take digital pictures for comparisons of any changing conditions. Make sure you remove any debris and or other materials that are not part of the roof. If you live in a wooded area, there may be branches of accumulated leaves that need removing.
If there are any issues that need repair, they should be dealt wit in a timely manner to prevent any further system deterioration. Repairs that are beyond what would be considered normal maintenance should be conducted by a licensed roofing contractor.
Keeping up on the maintenance and condition of your roofing system will help it to last, and help you to plan for long term replacement costs.