What military advantages and disadvantages did the Romans have

The main Roman advantage was their discipline which was unprecedented at the time and against the military forces which they were challenged against. This enabled them to conquer vast areas in Europe and become a dominant force at the time.

However, this becamse at the same time a disadvantage of their empire because when the empire grew to a certain size, iz became increasingly difficult to maintain and hold it together - this because their ultimate downfall as well.