President Bill Clinton nominated Roberts to the United States District Court for the District of Columbia on January 27, 1998, to a seat vacated by Charles R. Richey. He was then confirmed by the United States Senate on June 5, 1998, received his commission on June 23, 1998 and sworn in on July 31, 1998. He served as Chief Judge and a member of the Judicial Conference of the United States from 2013 until March 16, 2016, when he took inactive senior status.
