Roma seems to be the most Roman of all Roman deities. For centuries the Roman people worshipped her, sacrificed and prayed to her. On this coin of emperor Nero (54-68 AD) she is depicted on the reverse. She is sitting on a throne and holding a little Victory in the palm of her hand.
Roma was not 'invented' in Rome itself, however, but in Smyrna in 195 BC. At that time, the city was in a difficult political situation, because the Seleucid king Antiochos III demanded its surrender. Smyrna was not willing to give in, was looking for allies, and found Rome. To convince the Romans to send help, the Smyrnaeans quickly created a new cult and added Roma, the embodiment of all Romans, to their Olympus.
Not that it helped; the Romans stopped Antiochos only some years later when he started to conquer European Thrace.