As one reads about the daily lives of ancient Romans, one runs across the two major schools of philosophy: stoicism and epicureanism. These schools, along with other smaller schools such as cynicism, contended for the minds of the citizens of the Roman Empire. However, these schools were not proselytizing by nature. Citizens were attracted to them per individual tastes and mindsets.
Alongside this, one observes that the intellectuals among the ancient Romans, such as Cicero, were not great believers in the pagan gods of the day. The attitude to religion overall was that of customary common practice, rather than having a prepackaged set of beliefs which had to be digested by each follower. It appears that it was mainly near the Eastern borders of the empire that people were more prone to pay obeisance to their potentates and thus, had a more servile attitude towards their gods.