 In 1948, after a Communist newspaper accused him of illegal financial manipulations, Roberti successfully sued for libel, sending the reporter to jail for twenty months.On 6 October 1952, Roberti also assumed the position of legal consultor to the Secretariat of State.Pope John XXIII created him Cardinal-Deacon of "Santa Maria in Cosmedin" in the consistory of 15 December 1958, and then Prefect of the Apostolic Signatura on 14 November 1959.