It is true that ancient Roman artists borrowed freely from their Greek neighbors. But the Romans did develop their own styles in art. One example of Roman artistic innovation dating to the Republican Period is the portrait sculpture.
The difference between Greek and Roman artistic temperament is revealed in a comparison of the sculpture created by each culture. While the Greeks were content to idealize their images, the Romans often preferred depictions in stone and bronze that emphasized the reality of the person being portrayed. There are many portraits from the Roman Republican period that show real people represented with life-like clarity. To such an extent was this realism taken that one is tempted to muse that nothing escaped the insightful eye of the Roman sculptor - the subject appears literally "with warts and all" in many cases.
Some art historians believe that the vividly real portrait sculptures that appeared during the Republican Period were inspired by death masks. However, other scholars have argued that the death mask had little to do with the realistic portraits that became so important at this time. No matter what motivated Roman artists to create their images of "real people", the fact remains that these portraits are powerful visual evidence of the industriousness of the ancient Romans. Indeed, it seems fair to say that in some respects, the Romans wanted to create the world in their own image...
A Handbook of Roman Art
This book features individual chapters devoted to explaining the fine arts in ancient Rome - descriptions of architecture, sculpture, and wall painting are balanced by images. And the decorative arts are also represented, including metalwork, gems, jewelry, pottery, and glass.