サン・シール陸軍士官学校
Roudaire was born into a middle-class family. His father, François Joseph Roudaire, was director of the Natural History Museum of Gueret. After classical studies in his hometown, François Élie turned towards a scientific career in the army. He entered the Ecole Spéciale Militaire de Saint-Cyr in 1854. In 1864, he was assigned to Algeria as an officer surveyor, given the task of creating a geodesic and topographic survey of the colony. Operating south of Biskra, in Constantine Province, he explored the region's chotts, and was one of the first to accurately measure their depth, noting that many lay below sea level.