Biography.com: Roscellinus, Johannes: Four sentences about his life.
Catholic Encyclopedia: Roscelin: Article by M. de Wulf on this scholar, his teachings, and his tritheistic heresy.
Columbia Encyclopedia: Roscelin: Concise entry from the 2001 edition.
History of Philosophy: Roscelin: Short footnoted article on this medieval thinker and his place in history, summarizing four points of his doctrine.