Which of the following were Roman architectural innovations?

Most important among the structures developed by the romans themselves where basilicas, baths, amphitheaters, and triumphal arches.

Roman Architectural Innovations. Most important among the structures developed by the Romans themselves were basilicas, baths, amphitheaters, and triumphal arches. Unlike their Greek prototypes, Roman theaters were freestanding structures. The auditorium was semicircular, with movable seats at the orchestra level.