Being signed at the age of only 12, he travelled regularly by taxi from Tudela to the club's training facilities, until eventually moving to a school in San Sebastián.

Ros made his first appearance for the first team on 23 May 2009, coming on as a substitute for another youth graduate, Markel Bergara, in the early stages of a 1–0 away win against UD Salamanca.

[8] Ros scored his first goal for Real Sociedad on 18 December 2013, opening the 4–0 home win over Algeciras CF in the round of 32 of the Copa del Rey (5–1 on aggregate).

[12] A regular starter in his first seasons, Ros lost his starting spot midway through 2019–20, and suffered a knee injury which kept him out for six months in December 2020.

His older sibling Iñigo was also a footballer and a midfielder, spending the vast majority of his professional career in the third division and also representing Real Sociedad B and Eibar.