Roma have won their first two games of the season, while Juventus can only boast four points from a possible six.
Juventus have dominated the clash in recent times, winning their last three matches against Roma, but Allegri believes Saturday's encounter will be a balanced match.
"Tomorrow is the first direct clash against a Roma side that is doing well," Allegri told reporters.
"Facing Mourinho again is always a pleasure, he is doing a great job and shaping Roma in his own way. It will be a very balanced match."
Dybala will be making a return to Turin after joining Roma in the summer Allegri is looking forward to meeting the Argentine, who was Juventus' top scorer in all competitions last season.
"We spent some extraordinary years (together), with his game, he made everyone have fun," Allegri said. "Tomorrow, we will meet him again as an opponent, it is a pleasure to see him again."
Allegri confirmed that Leonardo Bonucci and Angel Di Maria have been ruled out of the encounter.
Juventus have won 10 out of their last 11 home games against Roma.
Mourinho led Roma to the Uefa Europa Conference League trophy last season, and he has strengthened the team with the signings of Nemanja Matic, Paulo Dybala, and Georginio Wijnaldum.