Walls and Ceilings - high humidity damage?? or roof??

My ceilings are cracking and there is mildew forming all along the outside perimeter of each room ceiling. I have single pane windows with storm windows, and there is condensation on them most of the time. Is this the cause of my problems, or is it the roof? Do I need a new one? The one on it is probably 25 years old. Upon going up into the attic, it looks as if the inside wood is dark and looks water stained on the North and East sides of the house.

Note: I rent and do not own this home. The owners are elderly and aren't quite up to par when it comes to resolving issues such as these. They don't know where to start when it comes to finding out the cause and leave it up to me. What kind of contractor should I have take a look?

You don't have enough ventilation in the attic.