From 1935 to 1940, André Rousseau worked at Dufresne Engineering and was in charge of overseeing the electrification project during the construction of the Wellington tunnel that passed under the Lachine Canal and the Pierre Le Gardeur Bridge in Montreal.

On an international level, he succeeded in giving weight to economic teams of the first delegations outside of Quebec in New York, London and Paris.

Although Rousseau was personally opposed to the nationalization of private electricity companies, he remained faithful to the government and sought a second mandate at the 1962 Quebec general election.

Although defeated on election night, by Fernand Lizotte of the Union Nationale (Quebec), Rousseau remained very active in the political arena.

He reentered politics during the 1976 Quebec general election as a candidate for the Union Nationale in Montmagny-L'Islet but was defeated by the liberal Julien Giasson.