Recruitment in the Auvergne

[Nathan Ross]

which Roman units might have been recruiting in and around the Auvergne

Malone shows XX (Chester) drew Tribunes and Centurians from the Rhone Valley.

Difficult question to answer, I think - there's very little evidence for the geographical origin of auxiliary soldiers after their units started recruiting locally. I would guess the cohortes Aquitanorum might be a possibility, or the various cohors Gallorum, which presumably drew men from all over the place. But the lack of large numbers of units drawing their titles from more settled provinces might indicate that the army preferred to recruit from the frontier regions (perhaps just because that's where the military bases were?)

Legionary tombstones often give a place of origin, or at least a tribe, but officers could have come from anywhere. By the first century I would think the Rhone valley was both entirely Romanised and quite wealthy, so an ideal place to find the ambitious provincial minor aristocrats that increasingly made up the Roman officer caste!