Roger Guérillot was born on 12 November 1904 in the 14th arrondissement of Paris, to a 21-year-old domestic servant, Marie Guérillot, employed by a family of the 16th arrondissement. Until the end of his life, Guérillot used two first names on legal documents, Léon and Charles, He had been a student at the École Spéciale des Travaux Publics before being hired by Michelin in 1928, to work as an engineer in their technical service centre in Paris. The historian Pierre Kalck claims that Guérillot was only a mechanic, dispatched to French Equatorial Africa in 1928 to work on the steamships. In 1935, Guérillot left Michelin and moved to Ubangi-Shari where he worked for the Society of African Mechanics and then the Society for Forestry and Industrial Exploitation. Following the invasion of France by Axis forces in July 1940, Guérillot joined the Free French. For his services he was awarded the Resistance Medal and the Commemorative medal for voluntary service in Free France after the war.
