... In your case, ALL the exterior walls are load-bearing. Especially if your 2nd floor is a finished floor. As this attachment on Load Bearing Walls says, even the Gable Ends can be load bearing.
In my house, which is a 2-story Colonial, the gable ends (of course) run parallel to the joists and rafters, and are built as load bearing. I guess it's possible that if your 2nd story isn't finished, or if you don't have a 2nd story, the Gable Ends may NOT be constructed as load-bearing.
If this is confusing you, that just shows you it would be best to consult a Professional ENgineer, an Architect, or a Building Contractor, in order to determine the type of construction you have.