You can join a roof to the top face of another roof and the wall below that roof if you select the wall as the target.
Revit intersecting roofs.
This is a general.
Use it to extend the dormer roof to the main roof.
In order to close off the end of the soffit i will create a new fascia sweep but i will host it to the soffit not to the roof eave or rake.
To create a dormer model required walls and additional roof.
You cannot join a roof to more than one top face of another roof.
You can join roofs to other roofs or walls or unjoin them if they were previously joined.
Revit roof tutorial and free file download.
Then follow these 2 steps.
9 join roofs add opening to create dormer.
The wall must be attached to the target roof and the target roof must be a footprint roof.
Download the working file for free to see mo.
This video goes over the steps to clean up two different roof elements.
This tool is located in the modify tab.
Use join unjoin roof tool.