Use the Modify Form command to extend walls up to a roof.
The Modify Form command is unique in that you must select the element you want to extend the form to before you select the element you want to extend. In this example, we will extend walls up to a roof.
1A. Using CONNECT Edition:
Select the wall you want to modify, and from the contextual Modification menu click on the Modify Wall tool. Set the options to "Modify the Height of a Form" and the Method to "To Form Or Shape":
1B. Using V8i:
Select the Modify Form command from the Architectural tool panel and set the options to "Modify the Height of a Form" and the Method to "To Form Or Shape":
2. Left-click on the roof. It will highlight, then accept it with another left-click:
*** At this point, you must right-click (Reset) to get the command ready to select the walls you want to extend.
Select (left-click) the wall (or multiple walls) you want to extend up to the roof:
As you select each wall, it will be extended to the roof:
Finally, in this video a single wall is extended up to two different roofs: