Born on March 26, 1990, in Bourg-de-Péage, France (to a Moroccan father from the city of Al Hoceima and a French mother), Romain Saïss developed a passion for football at an early age. He grew up in a footballing family, with his younger brother Amine also playing at the amateur level.

At the age of 7, Romain Saïss joined AS Valence, where he rose through the ranks of the youth teams. His father, a passionate football fan, instilled in him a love for the sport and encouraged him to pursue his dream of becoming a professional footballer. Growing up in a family where football was central, Romain Saïss was inspired by the achievements of Moroccan legends like Abdeslam Lamri and Mustapha Hadji, motivating him to proudly represent his country on the field. In 2007, at the age of 17, he signed his first professional contract with AS Valence. He was then loaned to Le Havre AC and Clermont Foot, where he gained experience playing regularly in Ligue 2.