The entry level, easiest to obtain oilrig role is the roustabout. It is a role that requires a lot of heavy lifting, manual work, painting, sandblasting, loading, unloading and other intense physical work. As you gain experience, you grow from roustabout to roughneck.
These are the individuals who are responsible for the smooth and effective functioning of the drill. This involves raising it and lowering it as required when bits have to be replaced and performing routine maintenance tasks. There are roles in the middle of this spectrum as well as supporting roles, all of which are essential for the seamless functioning of the rig.