Brain Snacks: Tasty Tidbits of Knowledge
The only things we know about Béroul, author of the Romance of Tristan, are that he was named Béroul and that he wrote The Romance of Tristan in "about the middle of the twelfth century" (Fedrick, Romance of Tristan, Title Page). That's a fancy way of saying we pretty much don't know anything about him at all.
In the late 18th century, people started getting really into in the Tristan legend again after Sir Walter Scott wrote a summary about it in his discussion of a minstrel, Thomas the Rhymer, in Minstrelsy of the Scottish Border.