Okay you have a "leaking" problem of
sorts. 1) it could be condensation
from inadequately vented attic space
or......
You roof is leaking! You didn't mention
if this occurred all the time or only
when the weather was inclement. My suggestion check 3 things.
1) guttering is it clogged ,occluded or
not draining properly.
2) Is the roof leaking through the shingles or are nails sticking up and
or protruding through the shingles.
3) Check to see if valleys, flashing,
or chimney to roof penetrations are
properly flashed and sealed with mastic.
Only way to find out is to do some
inspections or hire a home inspector
to check possible problem areas.