I Wonder what time of Rome it is set in like has the Teutoburg forest massacre happened is there a Senate. Plus has the praetorian guard been Disbanded or are they still around.
Hard to say, thought there are few things ingame.
-We know they left Brittany generations before and some want to reclaim it: the romans left Brittany AD 410
-Bad history with the Visigoths generations before : they sacked/plundered Rome AD 410
-The old empire don't exist anymore : The fall of the western roman empire ended AD 476
Then we have the barbarians
-The vikings seems to be a thing and the danes are a great kingdom : the viking era started in the late 8th century and the danes had a great kingdom (Danelag) begining AD 865
To ur questions
-Teutoburg forest massacre happend AD 9, so this should happend long ago, even before the romans conquered parts of Brittany.
-The pretorian guard has been disbanded by Constantine AD 312 as he bacame emperor, there was no real successor unit, understandable as they were highly corrupt in the later years and liked to instal/control/kill the emperors.
-The senate, disbanded in the early 7th century IIRC, ingame it wasn't mentioned.
Thought, i don't think the game is all that accurate in terms of history.