Livy records the rites before battle.

Romani consules, priusquam educerent in aciem, immolaverunt.

The Roman consuls, before they led out [their troops] into the line of battle, offered sacrifices. 

Romani: Roman

Consules: consuls

Priusquam: before

Educerent: they led out

In: into the

Aciem: the battle line

Immolaverunt: they offered sacrifice