If Rome doesn’t fall to the Arab invasions, the Persians don’t either. Both were tired and exhausted from years of warring with each other. Both were extremely powerful empires and the Arabs had as much an advantage of invading at the right time as much as anything else

The Sassanids were way less stable than the Romans during the initial Islamic conquests. The Battle of the Yarmuk going the opposite way could easily set up the expansion of the Caliphate to be directed east rather than West and allow the empire more valuable recovery time. Once ensconced on the old Sassanid throne, I don't see a particular reason that There shouldn't be a similar detente between the Arabs and Rome as there was with their predecessors.