With each legion having 5,120 legionaries plus an equal number of auxiliary troops , the total force available to a legion commander during the Pax Romana probably ranged from 11,000 downwards . The more prestigious legions were stationed on hostile borders or in restive provinces tending to have more auxiliaries . With each legion having 5,120 legionaries usually supported by an equal number of auxiliary troops , the total force available to a legion commander during the Pax Romana probably ranged from 11,000 downwards , with the more prestigious legions and those stationed on hostile borders or in restive provinces tending to have more auxiliaries .