Quote Originally Posted by vartan View Post
Didn't answer the question.
They were of similar quality as the Roman legions themselves, similar equipment, organized similarly but in smaller groups, similar length of service requirements (25 years). The main distinction is that they were not all Roman citizens and instead gained citizenship after their 25 years. Their role was to provide specialized combat services to the Roman heavy infantry and cavalry. After all, pretty much the 2nd best archer in the game is an auxilia unit and the current depiction of the heavy infantry cohorts stat them to be basically Romans except no missiles and spears instead.

The auxilia arms of the Roman Army came to play an important role over the course of the 1st Century, and by the beginning of the 2nd Century they had, in many senses, surpassed even the legions in usefulness. Nonetheless, in the 1st Century AD the reputation of the auxilia was marred by several bloody auxiliary revolts. From the years 6 – 9 AD Illyrian and Dalmatian auxiliaries in modern Yugoslavia sided with only partially conquered, anti-Roman tribal factions, and started a bitterly fought guerilla war that seriously depleted Roman manpower. Only a few months after the Illyrian Revolt was put down, in September of 9 a former native auxiliary commander, the Cheruscan German Arminius, lead three Roman legions and some auxiliary units into a trap in the Teutoberg Forest of Germany. The Romans were slaughtered and panic ensued throughout the Empire, even in Rome herself, at the magnitude of the crisis. The Roman frontier was consolidated and restored along the Rhine by Germanicus half a decade later. In 68, the last year of the reign of Emperor Nero, Batavian auxiliary commander Julius Civilis started a revolt amongst a number of Germanic peoples and this movement was put down only with great bloodshed and human tragedy. There were also a number of isolated instances of rebellion – the tragic adventure of the Usipi at the end of the 1st Century being a famous example.

Many of the auxiliary rebellions occurred because the troops’ local sympathies were stronger than their Roman sympathies. Julius Civilis, a proud citizen of the Batavi people, started his rebellion to avenge the honor of fellow countrymen who felt they had been slighted by the Emperor. Likewise, the Illyrian rebels of the beginning of the Century were stationed amongst their ancestral lands, with their families and villages close at hand, and finally decided that the liberation of that which they loved was more important than their oath to the Empire. In light of this, starting in the late 1st Century we find that Roman emperors and generals consciously attempted to post auxiliary regiments far away from their native lands; thus, we find Britons in Dacia, Syrians in Britain, and Spaniards in Egypt. Though many of these troops ended up marrying local girls and probably learning their languages, their local sympathies would have never come close to the loyalty they felt to the Army and their comrades.

The auxiliary regiments fought gallantly in all the great wars of the 1st and 2nd Centuries AD. Spanish, Celtic, and German auxiliaries participated in the Roman invasion of Britain (43 – 51 AD) and afterwards formed the most active part of Britain’s garrison. The much-vaunted cohorts of Batavian infantry proved more than a match for even the boldest of woad-painted Britons in the invasion. A number of auxiliary units, particularly cavalry, served with distinction in the civil war that erupted with the death of Nero (68 – 69 AD) as well as during the contemporary First Jewish War (68 – 73 AD). Auxiliary infantry of German origin formed the vanguard of Julius Agricola’s army during his invasion of Caledonia in the 80’s, occupying a role that had always previously been filled by legions.
http://www.historum.com/war-military...n-auxilia.html

They weren't simply cheap bodies but support units expected to be the best soldiers to provide the best possible services.