Roof leaks are associated with problems in the roof covering, but we have various vents disrupting this surface. Plumbing vents are one of those penetrations. Older lead flashing on plumbing vents are giving way to the new plastic vents, which may not be so great.
A popular retrofit for older homes is new windows, but you may not be installing them correctly. Proper flashing is one concern.
If you have a window or door that sits flush or proud of the wall, you probably then have trim sitting on the wall. This can be a problem area for moisture.
Part of your plumbing system penetrates the roof. These are the vents, and they could be a source of leaks in the home.