Attach the roof tripod to the edge of your roof. Follow the manufacturer’s instructions. Adjust the shaft on the roof tripod so that it sticks out over the edge of your roof.
Measure the distance from your roof to the ground. Double it. Add the height of the roof tripod to the result. Add another 10 feet. The result is the length of rope you need for your pulley system.
Attach both clamps to the tripod shaft, one above the other, following the manufacturer's instructions. Clamp one of the tripod clamps around the hook in one of the pulleys. Tie one end of the rope to the other clamp.
Thread the rope through the unattached pulley, the one still on the ground. Then thread the rope through the first pulley. The rope will now run from the tripod clamp, where it is tied, down to the ground, around the pulley there, and back up to the tripod, where it wraps around the pulley attached to it. The free end of the rope hangs down from this pulley.
Push the hook of the pulley that is on the ground through both ends of the rope hammock. The hammock will now serve as a net for holding the things you wish to bring to the roof. To lift it, just pull on the free end of the rope. Make sure that the hammock is large enough to wrap fully around the largest object you have to lift.