The Romans appeared to have an interesting dychotomy with respect to human sacrifice. They despised it, and used it to show how "barbarian" their enemies were. For example, the Carthaginians were baby-sacrificers, and the Druids of Gaul burned men alive in wicker cages... which civilized Romans would never do.

And yet--

Rome did practice human sacrifice.

After Cannae, the Romans buried a Gallic man and woman in the Forum.

Roman gladiatorial games originated as funeral rites.

Roman battlefield commanders could commit a "devotio" and sacrifice their lives for victory.

It seems Roman religion had two levels of Gods. Gods of the "above" world, such as the Olympians, and Gods of the inferno, the underworld. While it was an extreme sign of barbarism to sacrifice human lives to the Olympians, who preferred the scent of burned animal sacrifice, the Gods of the underworld DID demand blood sacrifice, and that could be human sacrifice at times.

It's very interesting to consider how the Roman mind could consider how some human sacrifices were barbarous, but not others. It distinctly corresponds with the Roman idea that religion was rituals that had to be performed precisely. Human sacrifice, therefore, to the wrong Gods, would be the "wrong" ritual and thus would offend the Gods....