The veteran, tapped to fill the midfield void a left by Sergio Busquets's departure for Major League Soccer's Inter Miami, returns from Girona to the club where he launched a career that has also taken him to Chelsea, Valencia, Stuttgart and Southampton.
"The emotions and sensations are very nice," Romeu told reporters after club president Joan Laporta introduced him at the Los Angeles Memorial Coliseum, where Barcelona are preparing for their pre-season tour.
"Having the chance to return home and continue growing is an intense dream. It's one of the most exciting challenges of my career and the opportunity comes at my best moment," added Romeu, whose signing, which will keep him in Barcelona through 2026, was announced on Tuesday.
Romeu departed Barcelona 12 years ago, in part because Busquets, another youngster from the youth academy but a little more than three years older than Romeu, was establishing himself as a midfielder who would go on to become one of the best playmakers in Spanish soccer.
"He is a player who has marked an era," Romeu said of Busquets, who later Friday could make his debut for Inter Miami alongside Argentinian great Lionel Messi.
"He is the best '5' we have been able to see for as long as I can remember and arriving just after his farewell is a nice challenge that excites me," Romeu said.
In recent days, Barca coach Xavi Hernandez had contacted Romeu by phone to let him know that he was his pick for that position.
Officials of the cash-strapped club confirmed on Friday that with Girona reluctant to part with the player they paid the amount of Romeu's termination clause, which Spanish media put at $3.4 million (£2.65m).
Romeu is the reigning Spanish champions' third signing for next season, after German midfielder Ilkay Gundogan and center back Inigo Martinez, who were released after finishing their commitments with Manchester City and Athletic Bilbao.
Barcelona open their US tour on Saturday with a friendly against Juventus in Santa Clara, California.
They return to Los Angeles for a match against Arsenal on Wednesday.
On July 29th they'll face Real Madrid in a 'Clasico' before closing the tour on August 1st against AC Milan in Las Vegas.