To be honest, adding the word "pagan" just seem needlessly divisive. When I read about the past, nobody is going out of their way to point out that it's Pagan.
Do you believe that Goy/Goyim is similarly divisive? Or Kafir? And I’m not sure what books you’re reading, Pagan vs Christian Rome is a common distinction if the context hasn’t already made it obvious (such as here).