31 October 475 A.D., Romulus Augustus was crowned Emperor in Western Roman Empire.
His name (from Romulus, the founder of Rome, and Augustus, the first emperor) seemed to be promissory of a new golden age in Roman Empire. But soon he was nicknamed Agustulus (little Agustus in Latin). Too young to rule the Empire (just 14 years old), he was actually a puppet between his father´s polical ambitions and the land requirements from the Germanic chieftain Odoacer.
His deposition by Odoacer - 4 september 476 A.D. - is the milestone that marks traditionally the end of Ancient Romam Empire and the beginning of the Middle Ages in Western Europe. Anyway, Romulus Augustulus´ rule was a symptom of the Roman fall, but not the cause.
Here you have some different resources that help you to understand this complex period.