The Romans believe in evil spirits but I don't think they thought there were possesions. Evil spirts may have caused diesies but they didn't accually posses the person. Pagan Priests may have been order to please spirits in a particular place but we have to remember that the Roman Pagans had a different deffination of the "Nature of evil" Christianity estalished stirct guide lines of evil, with all evil falling under Satan's command. With Polytheism "evil" is alot more blurred.
So no, I do not believe Roman Priests preformed exorsicims on people, but I could be wrong.
Zeke