Was the Persian Empire actually ruled by Romans?

Completely potty idea. NO.

Byzantine Constantinople was.

Dear Friend, you surely meant the second Persian empire " The Sassanids: since the first Persian empire was "Achaemenids" which was ended by Alexander 300 hundred years before the roman empire establishment. anyway, there was no King or leader in Persia that could be Roman. in fact most of the times the went to war to each other, if there was a roman leader there shouldn't be so numerous wars. for example, shapur the first, defeated one of the Romans emperor, killed its successor and captivate the third one which was Valerian. But there could be some one you may asking about. Kavadh II which was son of Khosrow II ( Khosrow Parviz) actually her mother was the daughter of the Roman emperor and he made a coup detat in the persian empire and killed his father and most of his sisters and brothers. after him downing of persian empire begins until it captured by the Arabs.

No. That is rediculous. Why would Persian knights and cavalry archers slay Roman Legions and Cavalry for a living for atleast 600 years if Romans ruled Persia? Why would the Emperors of Persia so promote Zoroastrianism instead of Roman Paganism if they were Roman? Why would Roman emperors like Valerian be captured and humiliated if Persia was ruled by Romans?