The 22-year-old midfielder's existing deal had been due to expire at the end of this season and he will sign his new agreement in the coming days.
The terms will also include a €30million release clause, which could climb to €40m.
Roberto has spent his entire professional career with the Catalan club, making his debut in a 3-1 win over Malaga in the final La Liga fixture of the 2010-11 season.
He has since made 20 first-team appearances in the Spanish top-flight, most recently coming off the bench during Barca's 3-0 victory over Elche last month.
Roberto has scored a total of two goals in all competitions.