Born on a farm near Ville Platte, then in St. Landry Parish (since the seat of government of Evangeline Parish), De Rouen attended private and public schools, and St. Charles College in Grand Coteau, Louisiana.

De Rouen was elected as a Democrat to the Seventieth Congress to fill the vacancy caused by the death of Ladislas Lazaro.

Fellow Democrat Vance Plauché, a campaign manager for Governor Sam Houston Jones of Lake Charles ran without opposition for the seat.

De Rouen served as chairman of the Committee on Public Lands (Seventy-third through Seventy-sixth Congresses).

He served in the state banking department in Baton Rouge, after his retirement from Congress until his death.