The young Paraguay international returns to Spain after enjoying a prolific spell on loan with Sporting Gijon, while the Italians will have the right to buy the star back.
Real Betis has secured the services of Antonio Sanabria from Roma for a transfer fee of 7.5 million euro ($8.3 million), with the 20-year-old signing a five-year deal for his new club.
Roma will also receive 50 percent of any future transfer fee should Betis sell the Paraguay international, while the Serie A side have also included a buy-back clause, which allows them to re-sign the striker for €11 million ($12.