Bonus room walls to roof

when the roof is provided by the house below and you have bonus room over the garage, lets say.  How do you get the walls in the bonus roof to extend to the roof? 

You have to do the roof on the highest floor. 2nd floor or Bonus roof, etc.
Choose 'multiple floor' and both floors will appear as long as you have the stacked and modeled correctly.
Once you have them stacked and model add the roof. Then
Edit the walls and choose 'top of wall' and select 'fit to roof'.

One way is to give the roof energy heels, if you need more height, and height you want,  Then do your trusses as attic trusses.

 

Or if your doing a second floor , you put the roof on the second floor.   

 

If it is for 3d you can just use "adjust" and adjust the wall up to cover 2nd floor.

 

This is one of those thing, of draw it like you are going to build it.  I'm guessing your doing 

trusses for the bonus room.   Also this way you can do "fit to roof"  to go to roof

You may find this video from the SoftPlan YouTube channel helpful: https://youtu.be/HuF...CQ75kSvEUz8hLso