Is the ridge line vented? Here in Canada we have condensation problems, freeze, thaw, freeze thaw so moisture & condensation build upcan rot a roof. It's common to vent the ridge line & soffets to allow circulation. I can see your soffets are open, but could not see if the ridge cap is the vented type or not. Your ceiling is open so plenty of circulation there & i see the big fan in the back wall.