JTMSonny

I need some help and direction.  I understand floor plans and the basics.  I'm a user for about 6 years.  I draw existing houses and try to get them as accurate as possible.  I struggle with roofs  and today dormers.  I can place a dormer in the attic without issue.  I want to place it on the 2nd story, but the roof starts on the first story.  Think shoebox with and 8/12 pitch, with a smaller second floor.  When I add the dormer the interior walls of the second story return to OSB.  If I take the dormer away the room returns to sheetrock.  Can someone point me to some specific videos or help?