Raised in Montauban,  France, Valentin Rosier gave his first steps in football playing for Rodez AF. His capabilities grabbed Dijon FCO's attetion, club for which he started playing in the Ligue 1 and as a consequence has already been called for various times for the U-21 French National Team.

Rosier suffered an injury which kept him off the pitch for the last part of the 2018/19 season but Sporting CP saw a big potential in him as a right-back. Rosier is now playing full-strength for the Main Squad.

His Lion tattoo is his promise that he is a Lion at heart.