The clubs did not disclose the transfer fee for Ibanez, who joined Roma from Atalanta on a permanent deal in 2021.
Ibanez scored three goals in 48 games for Jose Mourinho's team last season.
"Welcome to Al-Ahli, Roger!" Al-Ahli posted on messaging platform X, previously known as Twitter.
Al-Ahli have named Matthias Jaissle as manager on a three-year deal after Red Bull Salzburg sacked the German coach.
Ibanez becomes the latest addition to Al-Ahli, who returned to the Pro League following a season in the second division, after Riyad Mahrez, Roberto Firmino, goalkeeper Edouard Mendy, Alain Saint-Maximin and Franck Kessie.
The Saudi Public Investment Fund (PIF) has announced a Sports Clubs Investment and Privatization Project involving the league champions Al-Ittihad, Al-Ahli, Al-Nassr and Al-Hilal.
PIF owns 75% of each of the four clubs, while their respective non-profit foundations own 25% of each.
