He enlisted in the United States Naval Reserve on 12 October 1940. After undergoing flight training, he was commissioned as an ensign on 27 September 1941 and reported to Scouting Squadron 6. Roberts was serving as a Douglas SBD Dauntless dive bomber pilot with the squadron aboard the aircraft carrier United States Ship Enterprise (CV-6) during the pivotal Battle of Midway, in which the Imperial Japanese Navy lost all four of the aircraft carriers it had committed to the battle in a crushing defeat.
On 4 June 1942, Roberts pressed home the attack on the Japanese aircraft carriers despite formidable opposition, contributing importantly to the success of the squadron and the entire task force, but did not return to Enterprise.
Presumed dead, he was declared missing in action on 5 June 1942. The United States. Navy destroyer escort United States Ship Roberts (Delaware-235) was named for Ensign Roberts.
She was converted during construction into a high-speed transport, and was in commission as such as United States Ship Roberts (APD-94), from 1945 to 1946.