I was thinking, did the Romans recruit locals or was it a pure Italian army? For example somehow they had enough men to cover all of Europe and even occupy forts in north Scotland.
I assumed they wouldn't recruit natives as they could rebel etc.
Depends on the time frame your looking at, but they did certainly made use local auxiliary forces as part of tribute to Rome. The whole of the Italian peninsular once it was conquered provided levvies for the Roman army as part of their tribute/taxation arrangements.
You interested in a specific point in history during the Republic or the Imperial years?