There are many Roger Williams quotes that exemplify freedom of speech and freedom of conscience. The following is my favorite quote on differing opinions. This quote is from the introduction to a paper he submitted in a town meeting that occured on 31 Jun 1648.
…all men are apt & prone to differ it is no New Thing in all former Ages in all parts of this World…either part or partie is most right in his owne eyes…–Roger Williams, 1648
The above is documented in “The Early Records of the Town of Providence, Volume 15”, published 1899.
Here is the full text of the submitted paper. (Recto is the front of a page, or the right side of a book. Verso is the back of a page, or the left side of a book.)