He was Naval attache in Brazil and Uruguay, and later he became close to the influential First Lady, Eva Perón, and served as her naval aide-de-camp until her death in 1952. He was then named head of the Río Santiago Naval Academy (close to the site of an important naval shipyard), though in August 1955, he was persuaded to take part in the coup d'état that toppled Perón on September 19. Credited with leading the Navy during the rebellion, Rojas obtained Perón's resignation and exile by commandeering the ARA General Belgrano - threatening to bombard the YPF refinery in Ensenada (then the nation's largest).