You need to create the bay window roof separately.
Make two roofs join in revit.
If desired set the lines of the second roof to be slope defining except the roof line that will be coincident with the.
You like these direct simple and to the point revit tips.
To create a dormer model required walls and additional roof.
Then from the modify tab on your ribbon use the join geometry command and select the 7 1 2 roof and the wall.
I believe this tools are not design for this purpose.
Select the wall and use the attach top base button to attach it to the underside of only the 5 1 2 roof.
If the eaves don t line up exactly the join will fail and with two different pitches it is likely that the eaves are not lining up.
For creating complex roof it might be easier if you create separate roof then use join roof tool to join them later.
Use join unjoin roof tool.
This tool is located in the modify tab.
Move the roof up and see if it will join.
Join roofs after you sketch walls and a roof for your design sketch another roof that you want to join to the original roof.
9 join roofs add opening to create dormer.
Click view tab create panel default 3d.
Using shape editing tools.
Select the roof and choose between raft cut and two cut in roof properties under rafter cut parameter.
It will join in the wrong order and you will need to use the drop down menu next to join to switch the join order.
This is the easiest way to do it.
Then follow these 2 steps.
If you use two cut you have to set a fascia height like illustrated below.
Click view tab create panel default 3d.
But i m not really sure if this is a best practice.
We have plenty more for you.
Join roofs after you sketch walls and a roof for your design sketch another roof that you want to join to the original roof.
Make the roof in one piece.