There's an interesting article by Holt Parker that proposed that the Vestals are in fact human sacrifices, just clearly disguised to be not 'human sacrifices'. The author (who's name sadly escapes me) suggested that they acted as pharmakos or literally scapegoats since the author noticed that:

• The virgin's chastity represented the defences of the Roman state. If it was breached then the state's defenses were also at risk.
• The discovery of Vestals breaking a rule always seemed to coincide with a major Roman catastrophe. It's noteworthy that the male half of the sinning is never mentioned or recorded.
• They always came from the elite yet we have no records of any families protesting or defending their daughters.

The condemned vestal was buried alive with a small amount of food. The idea being that if she truly was innocent then Vesta would save her. Since Vesta did not she clearly must have been guilty. Also this means no one has her blood on their hands.

One could add that there was also a male form of ritual sacrifice - the devotio. It was done by P. Decius Mus when he rode into the enemy lines willingly to be struck down. It's been argued that this too was a sign of a pharmakos ritual.