Religion was less strictly organised during Hadrians time being primarily a pagan era, and Mithraism was not at that time entrenched in military life (though it was known and beginning to expand). Pagan Roman soldiers were hugely superstitious, sometimes refusing to board ships for fear of angering gods, or even crossing rivers, seen as the domain of local gods who would extract terrible punishment for those that risked wading across, as if they were trespassing. There was a sort of "unit spiritualism" too, where centuries and legions were supposed to have a martial spirit that could be called upon for favour like any other deity. Of course the Imperial Cult was in place and had been ever since Augustus, although the figurehead was not necessarily fixed - soldiers would put images of their popular ruler ahead of a column as easily as the Caesar they were supposed to be loyal to. Remember that in Imperial times the post of Imperator ("victorious general") had ceased to be an honour installed by the men themselves, becoming a political office agreed by Senate and Caesar, yet by tradition the soldiers were as willing as ever to dedicate those senior men who were clearly blessed with divine favour (and the ability to bring victory and booty to the men).