The definition of Verism is the artistic preference of contemporary everyday subject matter instead of the heroic or legendary in art and literature; a form of realism. The word Versm is derived from the Latin word verus (true). The Romans meshed the cultures of the people they conquered and adopted it as their own, they borrowed and took and remade ideas from a lot of various countries. However Verism was very unique to them. Coming from an age of where art was made to honor gods and heroes, their art depicted everyday life.
The Greeks were obsessed with the perfection of the human body. The Romans preferred to capture the true essence of subjects rather than the unblemished perfection that the Greeks portrayed.
During the Roman age We also see a stray away from legends and gods, and focus more on Monotheism and Politics. I believe this is the major reason why Verism becomes so prominent in Roman Art. Because they started to loose a little of the emphasis on the gods and heroes and realized that they held no apparent control on the way they controlled their country.
Monotheism was a factor that lead to verism. Artisit were not so preocupied in creating art for an unkown god, so in order to fill the void they came to paint still lifes. The Romans were also very focused on a strong governement. To identify their political leaders they had to portray them as what they really looked like blemishes, furrows, warts and all. That is what versim is, and that is why the Romans were so deep in it's use.