You can see from this picture common causes of roof leaks.  Cleaning roof of moss, cleaning gutters, ensuring downspouts remove water from around foundation, all will contribute to a longer roof and more livable house.  Downspouts should end 2′ from house, 3′ or more if possible.  Moss should be removed once yearly.  All nail heads should be tarred.  All pipe flashings should be inspected for cracks yearly.  Crickets should be of sufficient slope to allow water to remove most debris (3/12 or greater).  If your roof leaks, call a roofer, or Revive Construction can recommend a licensed roofer to help.