Oliveira, 29, joins from Portuguese side FC Porto on an initial loan deal until 30 June 2022.
As part of the agreement, an option has been included that would enable the Giallorossi to make the transfer permanent.
“It’s amazing to be here at this great club,” Oliveira said.
“Roma have always shown a real interest in me and now I want to try and immediately help the team to achieve all its targets and continue to develop the right mentality.
“I am certain that my new teammates, alongside whom I cannot wait to start working, will help me continue to improve too.”
Oliveira is a full Portugal international, having represented his country at last summer’s European Championships.
A product of the Porto academy system, he has won six trophies during his time at the club.
He has previously had stints in his homeland with Beira-Mar, Penafiel and Pacos de Ferreira – while he has also experienced overseas loan spells in Belgium (with Mechelen), France (Nantes) and Greece (PAOK).
“Sergio Oliveira is a player that will add quality and character to our squad,” said Tiago Pinto, the club’s General Manager.
“He has won a lot during his career and has gained experience at the highest levels, representing both his club and his country in some of the most important competitions in the world.
“His desire to join Roma was decisive in us being able to find an agreement: we believe it is very important that we continue to bring in players that are eager to play for this club.”
An all-action central midfielder capable of contributing both in defence and attack, Oliveira will wear the No. 27 shirt for the Giallorossi.
Welcome to the club, Sergio!
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