While many roof problems can only be identified by actually walking the roof or leaning a ladder up against the eaves, some defects can be easily seen from the ground. Be sure to view all sides of the roof. In older neighborhoods with tall houses that are close to each other, it may be necessary to walk a fair distance down an alley to get a good look at the roof.
Look for any irregularities with the roof: shingles that look curled from the ground indicate an old roof. This type of curling almost always happens on the south side first, so pay special attention to that side.
This one is huge. Make sure water is properly directed away from the house. Look for proper gutters, downspouts, and downspout extensions. They’re not required, but they certainly help. Also, check to make sure the earth slopes away from the house. Water draining toward a house can lead to big water problems in the basement or crawl space, as well as foundation problems.
Look at roof lines as well; if water gets concentrated against the house, the potential for water intrusion goes up. The photo below shows a good example of several roof surfaces concentrating water in to a small area right up against the house.