If I was writing a story about the Romans and I knew next to nothing about the Romans, I would do A LOT of research. Personally, I’d probably start by outlining what I need to know first in order to write the story, and then I would google those topics and read basic encyclopedia entries on them. After that, I would head over to my best friend the Public Library and find 3-5 books on aspects of Roman culture that would most apply to my story. However, if this story is more involved with Roman politics/conquests/military/etc. that would require further research, I would also read up on historical events that are similar and/or relevant to the story. Lastly, even after beginning to write this story, I would check aspects of cuisine, clothing, etc. with Roman culture. Man, that sounds like a lot, but at least the story will be vaguely historically accurate.