If you are adding a new range hood over your stove and plan to vent it out through the roof you will need to get an adequately sized duct that will run all the way up through the ceiling into the attic and all the way up through the rooftop where it will be connected to your roof top vent.
Venting cooker hood through roof.
But the rule of thumb is to route it the shortest and straightest path to daylight.
Start in the attic and drill a hole through the roof in the desired vent location.
Most of the time this will be a vent in your wall or soffit.
Try to keep it close to the fan location.
There is proper flashing for flat roofs and a roof cap that has screen around it to keep insects out.
Venting hoods or ducted hoods either connect to an outside source of air or filter the air.
A cooker hood in place above a gas hob when the fan is switched on is sucks all the steam generated by any items cooking or boiling below up upwards through one or more ducts or sections of pipework to a place where it can be vented externally.
If you want to replace the range hood and exhaust fan above your stove and vent it to the outside and the stove is against an interior wall you have several options.
Leave the drill bit sticking through the roof so you can find the hole.
Self help video on ducting your vent a hood kitchen ventilation unit.
Installing a new roof vent will require either hiring a roofing contractor or doing it yourself provided you are handy and can exercise proper safety precautions while on the roof.
Step 1 ventilate exits when venting your exhaust hood you have choices.
Many times your choice depends on where your range is located.
You can choose a ceiling or a wall installation to exhaust the smoke and smells from your home.
Vent through the roof run duct work through the attic then attach the stove vent to a roof cap.