ESPN reported last week that Barca had agreed a deal with the Brazilian club and Roque, 18, has penned a contract with the Catalan club until the end of the 2030-31 season, and he is set to link up with his new teammates next summer.
Roque's release clause has been set at €500m.
Roque becomes Barca's third signing this summer following the arrivals of Ilkay Gundogan and Inigo Martinez as free agents after the expiration of their contracts with Manchester City and Athletic Club, respectively.
ESPN reported in June that Roque had emerged as their top target. Negotiations, led by sporting director Deco, accelerated soon after.
Roque caught Barca's attention after starring for the Athletico and Brazil youth teams. He helped his club reach the final of the Copa Libertadores last season and recently earned his first senior cap for his country.
The teenager has scored 22 goals in 65 appearances for Athletico, including six in his past six games.
"Goals," Laporta told Mundo Deportivo on Tuesday when asked what Barca can expect from Roque.
"He very much has his own style. You can't really compare him with [retired Brazil strikers] Ronaldo or Romario. He is someone that is deadly with both feet inside the box.
"He is different to what we have had here before. If you had to compare him to anyone, it would be Ronaldo, who was a force of nature with us. [Roque] has bags of potential, is young, powerful and Brazilian."