He worked on lens design and crystal optics, inventing the Rochon prism polariser.

In 1769, Rochon was part of an expedition under Ensign Grenier to find new, quicker maritime routes between Isle de France and India.

On 30 May 1769, the expedition departed, with the corvettes Heure du Berger, under Grenier, and Vert-Galant, under Commander La Fontaine.

They sailed through the Maldives and arrived at Malabar coast on 29 July, and eventually at Pondichéry on 6 August.

He continued to Diego Garcia, where he arrived on 24, and returned to Port Louis on 6 October.