Another way to do what I think you want is to use a roof to trim the end of the wall. You can use the Trim to roof command and then you don't need to keep the roof in the file. Or you could trim using Solid Element Operations (SEO) which will maintain the relationship between the wall and the roof which is useful when you are still playing with the design.
Erika
Architect, Consultant
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
AC5-18
Onuma System
"Implementing Successful Building Information Modeling"