role of Roman centurions

[Stackferret]

You might like to have a read of a translation of Vegetius - 'De Rei Militari'. Although he is very late (4th/5th century CE) he actually says that he made use of books written by 'The Ancients' (which haven't survived through to today) and were probably written around 1st BCE/1st CE. The only real problem with him is to make sure you know when he is referring to the earlier writers and when he is referring to the Army set-up in his own time.
He seems to be advising his (unknown) emperor of means of maximising the Army's efffectiveness at a time when they were short of men.
Hope this helps.
Dana