I was quit surprised watching a roofer doing a little job on the side on a neighbour's house, he propped his ladder up the side of the house, jumped onto the roof then quickly slid up a tile to make a hole for a foothold, and proceeded diagonally across the roof, sliding up every 3rd or 4th tile as he went, occasionally he hit one that was nailed so moved to the next one and carried on going ...
You could tell he was very comfortable working on a roof, whereas I move at the speed of a sloth when I'm up there, with three limbs in contact with the ladder(s) at any one time.