The men who filled the office of Legate were drawn from among the senatorial class of Rome. There were two main positions; the legatus legionis was an ex-praetor given command of one of Rome's elite legions, while the legatus propraetor was an ex-consul, who was given the governorship of a Roman province with the magisterial powers of a praetor, which in some cases gave him command of four or more legions.
This rank was also the overall Legionary commander. This post was generally appointed by the emperor. The person chosen for this rank was a former Tribune and held command for 3 or 4 years, although he could serve for a much longer period. In a province with only one legion, the Legatus was also the provincial governor, but in provinces with multiple legions, each legion had a Legatus and the provincial governor (who was separate from the legions) had overall command of them all.