what is the job of the Sherpas in this climb? What very important take with the ropes are they assigned to do?

Sherpa's carry gear and help guide the foreign guests up and down the mountain. They are frequently lifesavers of people who get in trouble. They also do prep (grunt) work setting up ropes and ladders. Ropes are used as a safety aid when climbing through really dangerous sections of the mountain; Hall typically relies on fixed rope lines through the "Death Zone" which sherpas set up.