Built for service during World War II, the ship was launched in June 1944, commissioned in July, and acted as a transport and as a replenishment carrier.She was powered with two Skinner Unaflow reciprocating steam engines, which drove two shafts, providing 9,000 horsepower (6,700 kW), thus enabling her to make 19 knots (35 km/h; 22 mph).By the end of the war, Casablanca-class carriers had been modified to carry thirty 20-mm cannons, and the amount of 40-mm guns had been doubled to sixteen, by putting them into twin mounts.She was launched on 2 June 1944; sponsored by Mrs. William Sinton; transferred to the United States Navy and commissioned on 6 July 1944, with Captain Percy Haverly Lyon in command.She then underwent several transport missions, first departing from San Diego on 13 August, carrying a load of 287 passengers and 71 aircraft bound for Manus Island and Espiritu Santo.She began operations on 4 July 1945, along with fellow escort carriers Admiralty Islands, Hollandia, and Thetis Bay.[6] Following the end of the war, Roi joined the Operation Magic Carpet fleet, which repatriated U.S. servicemen from around the Pacific.