Safety Harnesses and harness systems used for working at heights are normally a parachute type harness, attached to a flexible lanyard, which is then connected to a temporary or permanent anchor point.
The lanyard should always restrict falls to less than two metres and the roof anchor must be positioned extremely carefully to avoid any risk of a longer fall.
An alternative to lanyards are inertia reels. These work like a seatbelt. The user can descend gradually in controlled manner but if there is a sudden movement it will lock to arrest the fall.