There’s a great article on Roger Williams at American Creation, a new blog devoted to studying religion in early America. (Disclaimer: I contribute articles on the Puritans for this blog from time to time.)
Williams was a complicated character. He caused the Puritans of Massachusetts nothing but trouble, yet he was so charismatic and charming they could not bring themselves to punish him for years.
The article at American Creation tells most of the story. I’ll just add that Williams not only challenged the bases of Puritan theology, but also claimed that the royal charter that created Massachusetts Bay Colony was null and void because it was granted by King Charles, a sinner and false king, who had no earthly authority.
Williams would have had the Puritans go back to London, rip up their charter, try to convert Charles, and get a new, valid charter. For Puritans trying hard not to arouse an already hostile king’s anger, this was too much.
Williams was supposed to be sent back to England in chains as a traitor, but John Winthrop, governor of Massachusetts Bay Colony, intervened. Williams claimed that Winthrop told him what was being planned, and urged him to escape secretly. Winthrop had every reason to detest Williams, but he did not. He saw Williams’ sincerity and youthful innocence, and perhaps had faith Williams would eventually settle down. They remained close throughout Winthrop’s life.
Williams took off for what is now Rhode Island, and many years later got his own royal charter. By that time (1663), he had undergone a radical change from a man who had excluded everyone but his wife from the list of the saved to a man who welcomed everyone as equal.
This is the Williams who is well-known and loved. The story of how he got from A to B is a fascinating one.