Robert Johnson was born in Dovercourt, Essex on 10 May 1868, the son of Vice Admiral John Ormsby Warren & Edith Renira Warren (née Twyford). He joined the Royal Navy as a Cadet on 15 July 1881 and was promoted to Lieutenant on 1 April 1891. He was appointed to the Battleship HMS VICTORIOUS as the Torpedo Officer on 29 September 1898.

On 31 December 1904 he was promoted to Commander and, on 5 January 1905, he was appointed to the Submarine Depot Ship HMS FORTH (Devonport Submarine Flotilla) followed by an appointment to the Submarine Depot Ship HMS HAZARD in May 1905. On 18 April 1906 he was appointed to Submarine Depot Ship HMS THAMES, Portsmouth, in Command and for duty with Submarine Boats. On 12 November 1906 he returned to HMS FORTH in Command and in Command of the Second Submarine Flotilla. Robert Johnson’s next appointment was to the Submarine Depot Ship HMS VULCAN at Sheerness in Command and in Command of the Submarine Flotilla to date 5 January 1909. Promotion to Captain followed on 31 December 1910. He was next appointed to HMS EUROPA in Command on 16 December 1913. In March 1914 he was appointed to HMS PRESIDENT, for the War Course.

On 1 August 1914 Robert Johnson was appointed to the cruiser HMS CRESSY in Command. HMS CRESSY was sunk by th German submarine U-9 in the Channel on 22 September 1914, together with the cruisers HMS HOGUE and ABOUKIR. Robert Johnson was lost in the sinking.

His estate was left to his widow, Grace Isobel Warren (née Pasley). He is commemorated on the Chatham Naval War Memorial on Panel No 1.