What is the significant event in Roman mythology involving a great flood?

The significant event in Roman mythology involving a great flood is indeed the story of Deucalion. This myth parallels the more widely known flood narrative from Greek mythology. Deucalion, the son of Prometheus, is often regarded as a figure who survives a catastrophic flood that the gods unleashed to cleanse the earth of human wickedness. He, along with his wife Pyrrha, is credited with repopulating the earth after the water receded, making their story central to themes of rebirth and survival in mythology.

In contrast, the other choices do not pertain to a great flood. The birth of Romulus and Remus focuses on the foundation of Rome through the legendary twins, while the destruction of Troy relates to the events surrounding the Trojan War—neither of which involves the specific notion of a flood. Lastly, the creation of the Roman Empire involves historical and political developments rather than mythological events like a flood. Thus, the story of Deucalion stands out as the correct response concerning the great flood in Roman mythology.