I have a two story box house. The attic has insulation under the floor. The 10 ft peak attic is for storage. Should I add insulation under the roof? Thanks, Steve

NO!

A roofline needs to breath to allow the heat accumulated in the hot months a way to escape/dissipate.

Floors insulated are the only safe,economical,proper way to keep the shingles from being damaged due to too much heat and condensation.

KBC

KBC gets the prize with his answer. You would only insulate the "roof" if you were making your attic into a heated living space. Your roof should be vented in the eaves and also at the peak or ridge. How deep is your joist cavity in the attic floor, you should try to get R30 or R 38 into the cavity. PINK Fiber Glass Insulation