I Copy and paste from another topic…
Really for Romans campaign in aoe2 there are so many options:
Constantine, the one who built the later Roman empire completing Diocletian’s reforms, many battles against barbarians and rivals (massentius and licinius), rise of Constantinople, Christianity etc …
Julian, last pagan emperor, defeated the alemanni in Gaul and was acclaimed by the army, his campaign against the Sassanids however was a mistake… Very dramatic character, kinda “how the mighty have fallen” like
Theodosius, both father and son, the first saved Britain from barbarians one last time and the son had to fight Magnus maximus, usurper in the same Britain of his father, and later unified the empire for one last time by defeating arbogast and eugenius
Stilicho, half vandal general, starts from Theodosius reign and defended Rome from being sacked before its time defeating goths, vandals, Alans etc. Betrayed and killed by emperor honorius thus condemning Rome against Alaric.
Aetius, Roman general and rival of Attila, would be the best choice to tell the Huns campaign from the other side, but not only that, he fought Boniface at the beginning of his career and other battles, followed the same fare of stilicho, murdered by jealous valentinian III
Ricimer, suebian patrician that was puppeteer of many of the last western emperors, could be a “bad guy” kind of campaign where you have to kill even the poor majorian but in the end being victim of a similar fate, still he defended successfully Italy from vandals and many other invasions
Majorian, last great western emperor, managed to reconquer Gaul, Spain and was ready to retake Africa before being murdered by ricimer, tragic guy, for sure would be a great pick, was friend of aegidius, the guy that would later create the kingdom of Soissons
For early eastern empire if you consider it:
Justinian, there already are custom campaigns about him, there’s variety since you can fight against Persians, the Nika rebellion, then against vandals in Africa the next scenario, then in Italy against goths, franks and alemanni, even in Spain… Both belisarius and narses could be protagonists
Maurice, again war against Sassanids, the Lombards in Italy and finally against Avars and Slavs invasion in the Balkans, important and underrated emperor, wanted to divide again eastern and western empires but followed a tragic end, killed by a centurion named phocas who would become emperor after the army’s rebellion
Heraclius, last Latin Augustus and First greek Basileus of Constantinople, could start from his father, an Armenian who became exarch of Carthage and then dethrone phocas the usurper in Constantinople, but the main focus of the campaign should be him resisting Avars and Persians sieging the city and then counterattack and reconquer all provinces lost to Sassanids from Egypt to Armenia, truly impressive accomplishment… Was the last Roman persian war, after that Muslims came but I’m not sure if to include this since after that every scenario would be about losing until heraclius death
After them it’s Byzantine history I’d say.