Odenathus saved the Roman Empire defeating the Sasanids under Shapur 1st. However let us say the Sassanids dedeated Odenathus and eventually took over the Roman Eastern provinces? What would have happened? Would they be able to hold onto their possessions or would the eventually Auerilian comes and push them back. Also let us say they held onto these rich lands what would the long term ramifications for this? I would say Rome would have collapsed early which has potential PODs. Another would be a stronger and richer Sassanid with no roman competitor to fight with in the Eternal War would be able to handle the rise of Islam. Maybe Islam never exist and Zoroastrianism dominates the middle east? Or maybe the Saasnids become Christians down the line?