A different Germanic war might possibly change the late Julian dynasty, giving us different emperors.
There still will be uprisings in Germania, just as they were in Gaul, but if the West Germanic tribes are romanized, they will rebal against unpopular governors or for popular generals claiming the imperial title. Not because they try to secede from the empire.
There were three signifacant languages spoken in that area:
~ Ingvaeonic or North Sea Germanic is the ancestor of Old Frisian, Old English and Old Saxon (red)
~ Istvaeonic or Rhine-Weser Germanic is the ancestor of Old Frankish, Old Rhenish and Dutch (orange)
~ Irminonic or Elbe Germanic is the ancestor of Old High German like Swabian and Bavarian (yellow)
This map shows Germanic dialects ca. 1 CE:
Since these language groups are also religious and cultural groupings, the Romans might use them for subdivision of Germania, so even if in this TL Germanian is a Romance language, it might have strongly different dialects.