Many different gods were important to various Roman people at various different periods in the history of the Roman Republic and Empire, a period that covers over 1,000 years of written history and involves many changes in religious belief and practice. Among the traditional Olympian pantheon, Jupiter and Juno, the king and queen of the gods were especially important, as was Pluto, god of wealth and the underworld, Ceres the goddess of grain, and Minerva, the goddess of wisdom. The lares and penates, the household gods, and Vesta, goddess of the hearth were important to everyday home religious practice.
Roman Gods are more war-like than Greek Gods. So while Mars' greek equivalent Ares is very unpopular, in Rome Mars is very popular. Jupiter and Juno being king and queen are important in both both Roman and Greek form. Even though Minerva is goddess of wisdom and strategy she is thought of as a 'bad omen' because when the romans conquered Greece they took the 'athena parthenos'-the most famous statue in all of greece, by stealing the statue they stole athena and turned her into Minerva, but Athena is probably the most Greek of all the gods and she lost her purpose. Neptune is not very popular either since the romans didn't like the ocean very much.
Hope this helps.