Well, to my knowledge, Romans referred to previous times as "during the rule of.." and then the name of the ruler at the time (post-republic), or "xx years after.." and then a historical event (a flood, earthquake, vulcano eruption, famine -famines were also given names, by the way - , a battle, good harvest, bad harvest).

The "real" AD/BC of the Roman civilisation was "xx years before the foundation of the city" (the city being Rome, obviously) and "xx years after the foundation of the city". I'm not sure wether these were terms used by the Roman (common) public though, or merely a more cermonial way of keeping track of time.