Map of the Roman Empire and its vassals, the Western Roman Empire and the Byzantine Empire and its vassals at their greatest extent in 117 AD, 395 AD and 555 AD, respectively.

Homework. As approximate as possible. I couldn't find any information on the Western Roman Empire's vassals, if it had any. All my information is from Wikipedia. (And don't tell me Wikipedia lies, because even if it does, so does the source of information you trust. Everyone does it at some point in their lives. Even me.)