Remember Bob Marley with a special hairdo. He was called a Rasta because he practiced Rastafarian religion which began in Jamaica in 1930. Most followers were poor people of African descent brought by the British in West Indies as labours. It is both a religion and a social movement. They were oppressed and it was a reaction to this oppression.
Rastafarians believe that their God is Jah who is in fact Haile Sellassie, the king of Ethiopia. They believe that Christ was black. The religion is not strictly religion but a way of life. It says that in every living being, a part of Jah lives and love and compassion for every human being.
Their prefer to eat the food is almost organic vegetarian self grown. They smoke the cannabis like many Sadhus in India and consider it as a very pious substance. It calms the mind and helps the smoker to introspect the self.