The 30-year-old returns to Serie A after spending last season on loan at Inter Milan, where he helped the club reach the Champions League final.
He is said to have declined a lucrative move to the Saudi Pro League.
“The welcome that this club and these fans gave me thrilled me and represents a further incentive to give everything for my new team,” Lukaku stated.
Lukaku is thought to have agreed to a wage cut in order to rejoin coach Jose Mourinho at Roma.
Mourinho handled Lukaku briefly during his first stint at Chelsea in 2013-14, before signing him for Manchester United from Everton in 2017 for £75 million.
“I had the opportunity to speak with the owners in recent days and I was struck by their ambition,” Lukaku added.
“Now we must work, be humble, and grow game by game.” I, for one, am eager to make myself available to my teammates both on and off the field.”
Lukaku rejoined Chelsea for £97.5 million in 2021 after joining Inter for £74 million in 2019. His homecoming was unsuccessful, as he has not featured for the Blues since May 2022.
Lukaku did not accompany Chelsea on their pre-season tour of the United States, and despite having three years remaining on his contract, he was not included in new manager Mauricio Pochettino’s plans for 2023-24.
“Knowing that Lukaku has chosen Roma can only be a source of great joy for all of us.” “With his arrival, we gain more experience, professionalism, and a desire to win,” said Tiago Pinto, Roma’s general manager of the sports sector.
“All of our decisions are always aimed at increasing Roma’s competitiveness.” It makes us very delighted to see the supporters greet Romelu with such excitement.”
Lukaku previously won the Belgian league with Anderlecht, the FA Cup and the Club World Cup with Chelsea, and the Scudetto, the Italian Cup, and the Italian Super Cup with Inter.