His next assignment (22 September 1931 – 22 December 1931) placed him on the Admiral's staff at the Baltic Naval Station, while in parallel he attended a technical officers training course at the Naval Academy at Mürwik. Rösing was then transferred to the 1st Schnellboot-Demi-Flotilla (23 December 1931 – 1 October 1933) where he commanded his first boat, Schnellboot S-15. During this command he attended two more training courses, anti-gas defence (4 February 1932 – 17 February 1932) and a Spanish language interpreter training vacation (5 May 1932 – 15 June 1932). He passed his Spanish interpreter test on 26 October 1932. From 4 November 1932 the end of his assignment with the 1st Schnellboot-Demi-Flotilla on 1 October 1933 he commanded S-3.
