Start in the attic and drill a hole through the roof in the desired vent location.
Installing exhaust fan in bathroom through roof.
Place the fan in the cut out hole so that the bottom edge of the fan is flush with the bottom of the ceiling drywall.
Cut a piece of drywall to make the ceiling hole the right size for your fan.
Slide clamps over the flexible duct at both the roof cap and the fan housing then slip the clamps over the tailpieces.
Attach the bathroom fan to the joist.
You will need a partner for this step as you cannot see the ceiling from this position.
Try to keep it close to the fan location.
Wrap the joints with duct tape.
Attach the drywall filler to a larger piece of wood set it in the hole and drive screws through the ceiling into the wood.
This old house general contractor tom silva shows how to properly install a roof mounted bath fan vent.
From up on the roof use a jigsaw or reciprocating saw to cut a 4 in.
If the hole is too big you ll need to patch the ceiling.
Leave the drill bit sticking through the roof so you can find the hole.