Here are all the possible dates the Roman empire could of ended which adds up to 15.
I 476: The Western Roman emperor is deposed and the Ostrogoth king Odoacer becomes king of Italy. Who pleads his allegiance to Julius Nepos the remaining Western Roman Emperor
II 481: Nepos is assassinated this the end of the Western Roman empire but is it the end of the Roman empire? The Ostrogoth king carries on pleading his allegiance to the Eastern Roman empire.
III 629: The Eastern Roman emperor Heraclius now styles himself as a Basileus which is the Greek word for king. From his forward the Eastern Roman empire becomes more Greek than Roman and in the not so distant future Catholics and the pope would call the Eastern Roman empire the empire of the Greeks. The Muslims are a lot kinder and will remember the Empire as Rum(Rome) which is more polite.
IV 756: Rome would cease to be a part of the empire after being reconquered by the East
V 797: The Roman emperor, Constantine VI is deposed by his mother, Irene who becomes Empress. Because of this according to the pope no one is Roman Emperor
VI 800: The Frankish Barbarian Charlemagne is crowned emperor of Romans by the pope in the city of Rome which is an insult to the true Roman emperor in Constantinople.
VII 811: The Roman Emperor, Nicephorus I acknowledges the Barbarian, Charlemagne as Western Roman Emperor and rules the west where Rome is.
VIII 1002: The last real Roman emperor in the West Otto III dies and now the title Western Roman empire is just a title held by German kings.
IX 1204: The Queen of cities Constantinople is sacked and the Barbarians from the West now rule Constantinople.
X 1371: The Eastern Roman Emperor, John V becomes a vassal to the Ottoman Sultan and the Roman empire is not really an empire if the emperor is a vassal to someone.
XI 1453: The Ottomans capture Constantinople and kill the last Eastern Roman Emperor. According to allot of people this is when the empire ends.
XII 1460: Morea an Eastern Roman successor state which is ruled by the dead emperor's brother falls to the Ottomans.
XIII 1461: Trebizond the last place which has claim to the Eastern Roman Empire falls to the Ottomans.
XIV 1806: The last German king with the title Roman emperor is deposed.
XV 1943: Mussolini, dictator of Italy and the so called restorer of the Roman empire is overthrown and murdered and the Roman empire with him.