He remained in the army during the interwar period, reverting to his permanent rank of captain and serving briefly with the Egyptian Army in the Sudan from 16 February 1919. Returning to England, Roberts attended the Staff College, Camberley, entering in January 1921, shortly afterwards being made an Officer of the Order of the British Empire (OBE), and graduating in December 1922. Among his many fellow students there were Eric Costin, James Gammell, John Priestman, Edward Alban, Merton Beckwith-Smith, Russell Gurney, Francis Nosworthy, Giffard Martel, John Kennedy, Ridley Pakenham-Walsh, Ralph Eastwood, Edwin Morris, Eric Miles, Robert Naylor, Thomas Corbett, Ernest Squires, Austin Miller, William Baker and Edmund Osborne, all of whom would, like Roberts, become general officers. He later served in Egypt in 1923–24 and with the British Army of the Rhine (BAOR). He transferred to the Royal Warwickshire Regiment as a major in July 1927 and served with the 2nd Battalion in India and the Middle East. His next appointment was as a General Staff Officer Grade 3 (GSO3) with the Iraqi Army and, for his service in Southern Kurdistan, was promoted to brevet lieutenant-colonel.