If necessary use the viewcube to spin the design to facilitate selecting the wall or roof edges.
How to join double pitch roof in revit.
Select an edge of the roof that you want to join and then select the wall or roof to which you want to join the roof.
Using shape editing tools.
Click modify tab geometry panel join unjoin roof.
Then follow these 2 steps.
1 check define slope to create a sloped roof.
Use join unjoin roof tool.
Use it to extend the dormer roof to the main roof.
Groin vaults for your single groin needs 3 create a flat roof no edges defining slope then use the roof shape editing tools add split line set heights see attached revit file.
9 join roofs add opening to create dormer.
This tool is located in the modify tab.
Whether you want a double gable roof with 6 pyramid shaped dormers or a simple gambrel roof the basics remain the same.
Then draw the arrow to define the slope direction.
We want to join this face to the roof.
With the join unjoin roof tool selected you need to click on the line of the roof which is on the face of what you want to join to the other roof.
You can use height or slope value specify the method and the constraint values from properties palette.
To create a dormer model required walls and additional roof.
Then select the face of the roof you want to join in to and then.
Http pbl stanford edu how to attach walls to roof objects in revit.