Roberts worked with Mercury for the entirety of the series, then quickly switched to Project: Gemini in time to work with Gus and co-pilot John Young as they prepared the “Molly Brown” for the first launch of the Gemini series, on March 23, 1965. Roberts and Grissom worked tirelessly on the Gemini craft, trying to give it the “feel” of a jet with a control stick. That philosophy took root, and the Gemini capsule was soon dubbed the "Gusmobile.” As one astronaut described it, “It felt like we were flying this one, and not just along for the ride.”
Roberts and scores of McDonnell-Douglas engineers spent the Mercury and Gemini years commuting between St. Louis and the Cape. After Gemini, Roberts stayed with McDonnell-Douglas while accepting assignments to the Manned Orbiting Lab, Skylab and development of the Tomahawk missile. By the time he retired, in 1989, he was chief design engineer and department manager of all McDonnell-Douglas electrical and mechanical design engineers.
With the advent of Skylab, Roberts was again splitting time between St. Louis and the Cape. His assignment was to coordinate the design and definition of electrical systems in the M-D hardware, to ensure safe connections between the M-D hardware and other contractors’ hardware. And soon, “I was again a member of the launch team for initial hardware module launch.”