In October 2009, shortly after making his Barcelona B debuts, Sergi Roberto was called by the Spanish under-17 team for the 2009 FIFA World Cup in Nigeria. On 5 November, before being substituted by Javier Espinosa in the 88th minute, he scored a hat-trick against Burkina Faso at the Sani Abacha Stadium in Kano. Spain eventually finished third in the tournament, with him and Atlético Madrid’s Borja Bastón accounting for eight of the team’s total goals.

On 10 November 2010, Roberto made his debut for the first team, playing the second half of a 5–1 home win against Ceuta for the campaign’s Copa del Rey (7–1 on aggregate). On 27 April of the following year he made his first UEFA Champions League appearance, coming on as a substitute for David Villa in the last minute of a 2–0 away victory over Real Madrid for the competition semi-finals’ first leg.

Roberto first appeared in La Liga on 21 May 2011, playing the full 90 minutes in a 3–1 win at Málaga in the season’s last round. His first start for the main squad came on 6 December of that year, against BATE Borisov in the Champions League group stage, as manager Pep Guardiola rested all his starters for the upcoming El Clásico: in the 35th minute, he opened the scoring in an eventual 4–0 home win.

Roberto made his debut for the under-21 side on 5 September 2011, playing the last four minutes of the 2–0 win in Lugo over Georgia for the 2013 UEFA European Under-21 Championship qualifiers. He received his first call up to the senior squad in March 2016, for friendlies against Romania and Italy. His debut took place in the former match on the 27th, as he started in a 0–0 draw in Cluj-Napoca.

In only his third official appearance for Barcelona’s first team, on 12 January 2012, Roberto scored his second goal, helping the visitors come from behind to win it 2–1 against Osasuna in the domestic cup (6–1 on aggregate). On 16 December 2014, also in that competition, he netted another, contributing to an 8–1 demolition of Huesca at the Camp Nou.

In 2014, Sergi Roberto started dating Israeli model Coral Simanovich (Pnina Rosenblum’s stepdaughter). They became engaged in early September, and got married in Tel Aviv on 30 May 2018.

In the 2015–16 season, after being reconverted by manager Luis Enrique and merely months after nearly being deemed surplus to requirements, Roberto appeared as a right-back in several games. In two consecutive matches against Athletic Bilbao in January 2016, one for the league and another for the Spanish Cup, he featured on the other flank in the place of injured Jordi Alba, going on to play in as many as seven different positions.

On 20 August 2016, Roberto started as a right-back and provided two assists in a 6–2 home defeat of Betis in the opening match of the campaign. On 24 September, from the same position, he again contributed with two assists in a 5–0 away rout of Sporting de Gijón.

On 8 March 2017, Roberto scored the final goal for Barcelona in the 95th minute as part of a decisive 6–1 home victory against Paris Saint-Germain in the second leg of the Champions League round-of-16, making Barcelona the first club to overcome a four-goal deficit in the competition. On 22 February 2018, he extended his contract until 2022.

In injury time of the first half of El Clásico on 6 May 2018, Roberto was shown a straight red card after punching Marcelo, in an eventual 2–2 home draw. He was first-choice right-back during the season ahead of newly signed Nélson Semedo, and his team won the national championship after a one-year wait.

Roberto’s mother, María Rosa Carnicer, died in December 2019, a year after being diagnosed with amyotrophic lateral sclerosis.