How long did the roman empire rule and who ousted the?

While Monc is technically right, the end of the empire was caused over a period of centuries by the increased pressure of the barbarian tribes (Huns, Goths, Vandals, etc.) on their frontier, along with the general collapse of the empire in its inability to sustain its reach through military might. Whether it was the will to maintain the army, whether it was economic in nature...there are a lot of theories. Suffice it to say that as the Roman Empire collapsed from pressures within and without, ultimately it simply gave way.