Born on 20 October 1760 at Lorry-Devant-le-Pont, in the Kingdom of France, Roget entered military service in the 7th regiment of "chasseurs a cheval" (light cavalry), on 13 May 1777, as a simple trooper. In 1793, as a "sous-lieutenant" he served in Custine's army at the Siege of Mainz. Later he served with Marceau-Desgraviers and Kleber to quell the Vendee uprising. By the end of uprising in the Vendee, he had reached the grade of adjutant general. Recalled to the Army of the Rhine and Moselle, General Desaix gave him command of the 13th Dragoon Regiment, which had achieved battle honors at Valmy four years earlier; at the Battle of Dierstein, he led the 13th in a charge and defeated the Austrian "Regiment D'Alton", taking two flags and five cannons. He then turned to Offenburg, where he chased out the Austrians and pursued them beyond Gengenbach; in the second action, he took four guns from the Austrians, as well as forty boxes of ammunition, and a large number of prisoners.