1.   For economic reasons, I planned to use the original plumbing stack.

2.   The dryer in that house vented into the vertical plumbing stack.

3.   Then shingle above and around the flashing just as you would for a standard roof vent or plumbing stack.

4.   They chose the closet, but the builders incorporated the plumbing stacks and ducts for a bathroom in case they ever change their minds.