Later, Roper would assume command of the USS Wisconsin (BB-64) for the closing months of World War II, succeeding Earl E. Stone. During that time, he led the Wisconsin in the Battle of Okinawa. For his service during the battle, he was awarded the Legion of Merit. Previously, he had been given a Letter of Commendation for his services in the South Pacific Area, during which time he helped plan the Guadalcanal and Solomon Islands Campaigns.