Generally, the Romans called any soldier that was equiped the same way as them "immitation legionnaires", generally it was because the Romans were very egotisitic and didn't really pay attention to the fact that they themselves copied other people in their armour and warfare, so make sure to take the description "immitation legionnaires" with a pinch of salt. It is true, though that Roman centurions and officers were used by other nations to train their soldiers in the Roman way of fighting because of the success of the Roman legions.