original question: What is the video game series that includes a video game expansion designed by [Ken Rolston]?
answer: the elder scrolls
answer type: Video Game Series.
auxiliary information: Ken Rolston is an American computer game and board game designer best known for his work with West End Games and the hit computer game series The Elder Scrolls. In February 2007, he elected to join the staff of computer games company Big Huge Games to create a new role-playing game. Ken has a Masters Degree from NYU, and is a member of the Science Fiction Writers Association. He has been a professional games designer since 1982.
[Ken Rolston] is best known for designing the video game expansion of what popular video game series?