Interior walls won't extend to roof

[Bob Levin]

Hi All. the roof pitch for this part of the house is (flat) 1/4" per foot. I have the " ceiling over this room " boxes UNCHECKED in the structure tab of the room specifications dbx. The interior walls of this section of the house still will not go to the roof.I have the "full gable wall" box checked on the appropriate exterior walls. Thanks much Bob Levin