What were nobleman's jobs and responsibilities?

None at all. taking a job would have removed his claim to be noble. A nobleman lived on the proceeds of LAND. he owned the land, and other people worked it and paid him rent. Any form of trade or labour was forbidden him. In fact, many noblemen were as poor as church mice and did a lot of the work on their own farms. In France (as opposed to England) nobility wascommon to all the children of a nobleman; so by the time of the revolution, the thousands of acres with which an aristocrat started had been divided and divided until a man could own a very small patch indeed and still call himself noble. Oddly enough, some of the nobles who sympathised most with the revolution were among the most wealthy; Lafayette was one of the richest men in France. But there is no doubt that the formation of the National Assembly was facilitated by the number of nobles who empathised with the common people.