Roberts spent much of his early career in New York City as a freelance commercial artist and director. He also worked as a photographer, with work displayed at the 1964 World's Fair, and contributed cartoons to Playboy and The New Yorker. He soon became a popular designer for animation, creating character model sheets for Terrytoons and UPA projects. Roberts' style, reflecting his commercial illustration background, involved flat but appealing forms and a minimal color palette; most of his characters were white blobs with occasional splashes of color.
For the Sesame Street comic strip, Roberts created Jasper and Julius, a comedy duo who would engage in debates over body parts, as well as Christopher Clumsy and Miss Fortune. These characters were eventually brought over to the show in season 4.
- see also: Poverty Pictures segments