His father was a lawyer who was arrested during the
French Revolution when Roussin was aged twelve. He left home in
Dijon and travelled to
Dunkerque where he enlisted as a cadet in the
French Navy in December 1793. He served from 1794 to 1797 on various frigates. In 1801 he sat and passed the
midshipman's exam following two lessons from the
hydrographer Jean Petit-Genet. His first posting as an officer was to command a
gunboat at
Antwerp, part of the "National Flotilla" of coastal ships, collecting in various
Channel ports for
Napoleon's planned invasion of the United Kingdom. By 1803 he was promoted to
ensign and embarked aboard the
frigate Sémillante under the command of Captain
Léonard-Bernard Motard. They would spend six years in the
Indian Ocean, based on
Réunion, preying on
British shipping bound to and from
India. The worn-out
Sémillante was paid off at
Mauritius in 1808 after sustaining damage in a fight with the British frigate HMS
Terpsichore. Roussin was promoted to
lieutenant and posted to the corvette
Iéna. A cruise in the
Persian Gulf and the
Bay of Bengal ended when the
Iéna encountered the British frigate HMS
Modeste off
Calcutta and was captured after a two-hour engagement on 8 October 1808. Roussin and his captain, Lieutenant Maurice, were exchanged at the end of 1809 and returned to Réunion. Roussin was appointed second in command to
Bouvet de Maisonneuve aboard the frigate
Minerve, a prize taken by
Guy-Victor Duperré. Roussin received a mention in Bouvet's dispatches for his conduct during the
battle of Grand Port in August 1810. However, the French success at Grand Port was only a temporary setback to British plans to conquer Mauritius and Réunion, and Governor
Comte Decaen finally signed a capitulation in December. Roussin was repatriated to France, where he met the Emperor, who confirmed his promotion to
captain and presented him with the
légion d'honneur. Roussin was posted to command the frigate
Gloire fitting out at
Le Havre. After training, he cruised in the
Atlantic Ocean from December 1812 to April 1813, taking fifteen prizes, including two
sloops. ==Bourbon rule==