1953 cape cod roof ventilation

I live in a cape cod house that was built in 1953. The previous owners put an addition on the back of the house. I have two dormers in the front. I have two leaks on the first floor. One in the living room near the window, and one in the dining room near the window. Both leaks are about two feet from the windows. I plan to reaplace the roof, and the gutters. Right now I have no source of ventilation in the front of the house. In the back I have a soffit, along with two turbine vents. Inside the house on the second floor I have a house fan. I would like to know any ideas on ventilating my attic space properly. Also I would like to know if its okay to have rolled rubber ashpault membrane on the back addition.