Hi Dave,
Please, check the pictures attached and follow the explanation. I used a hip connector for the example
For the clarity of the explanation, this hip connector has 3 pieces (each one of the directions of the pitch)
The shapes in red are showing the places where you can add a roof cutout, because each cutout is inside a single piece
The shapes in blue are showing the places where you can't add a roof cutout, because each cutout is not inside a single piece
Therefore, the rule is: you can't add a cutout if the cutout is touching the eave, ridge, etc, therefore you will receive an error message
In addition, if you have a dormer in the eave, the cutout will not work, because the cutout has a border, so in the eave case (#3 in the image), I suggest the use of a freehand roof, and contour the dormer (green roof in the plan)
Hope this helps
Patricia