Dybala is a free agent and has signed for the Rome club.
The attacker joined on a three-year deal, with his contract with the Bianconeri ending in June.
Dybala scored 115 goals in 295 appearances for the club after joining from Palermo.
Dybala said the days leading up to signing the contract have been filled with many emotions.
The determination and speed of the people made the difference.
I'm joining a team that is on the up, a club that continues to put in place strong foundations for the future, and a coach that I'm very much looking forward to working with.
There was a renewal of the contest between Europe and South America when Dybala scored a hat trick in Argentina's win over Italy at Wembley in June.
Giuseppe Marotta said that they were in talks to sign Dybala.
In the summer transfer window of the year, he was linked with a move to Manchester United or Spurs.
The club's first trophy was the Europa Conference League, which they won in the first season under the guidance of Jose.
"Paulo is a world- renowned player who has won major trophies and gained global renown, he will bring that class with him to Roma and I am sure that, with him in the squad, we will be even stronger and more competitive," said the general manager.
Dybala becomes the fourth signing of the summer, following the arrivals of former Manchester United player, Mile Svilar, and defender Zekicelik.
When he was joined last month, the Argentine chose to wear the number 21 shirt, which had originally been selected by Matic. The Serbian international is wearing the number eight jersey.
The Dybala deal was announced on Wednesday using videos of missing children as part of their social media campaign.