I know they had some sort of priestesses that were expected to remain virgins and punished with death if they didn't, but in day to day life what was considered beyond the pale when it came to making fun of their gods or not honoring certain traditions etc? Did they take it seriously or consider it more of a personal matter? Were there any punishments set down?
These priestesses were the Vestal Virgins, and were under a strict religious and moral code. Their ostensible 'role' was to keep the Fire of Vesta (the goddess of the hearth and home) burning but of course they held various other ideological functions. They would be buried alive for something as little as an accusation of being unchaste but otherwise led very comfortable and prestigious lives (Livy Ab urbe condita 2.42.11).
In the early Empire, there were some very stringent rules regarding blasphemy against the first emperor Augustus who was deified after his death. A good example of this would be from Suetonius, an ancient biographer who reports that the successive emperor Tiberius would have somebody executed simply for saying something negative about Augustus or even bringing a coin bearing his image into a toilet or brothel (Suetonius' Life of Tiberius 58)!
Aside from the Imperial cult in Rome, religion was an exceptionally personal matter, not at all like modern religions like Christianity or Islam in that people could generally choose how to worship their gods, and which gods to worship or not worship as it may be. The underlying idea was that the gods did exist and most people had fairly strong religiosity.
Some religious cults like the Cult of Bacchus were actually banned for their reputation as rowdy and disruptive to society, as well as for prominently including women in their wine-fuelled rituals.
Modern sources/further reading:
Rives, J., (2000). "Religion in the Roman Empire" in Janet Huskinson (ed), Experiencing Rome : culture, identity and power in the Roman Empire, 437-489. London.
Beard, M., (1998). Religions of Rome, Cambridge.