Why did roger williams leave massachusetts bay colony, and what did he do next?

He got banished. After leaving Massachusetts, Williams, with the assistance of the Narragansett tribe, established a settlement at the junction of two rivers near Narragansett Bay, located in present-day Rhode Island. He declared the settlement open to all those seeking freedom of conscience and the removal of the church from civil matters, and many dissatisfied Puritans came. Taking the success of the venture as a sign from God, Williams named the community "Providence."