1980s childrens book roman boy ?slave

I think from the 1980s,childrens fiction, cover had a boy on it I think, about a roman boy (?slave).

The Mystery of the Roman Ransom by Henry Winterfeld? The copy I read was from the '80s although the book is older.

Not from the 1980s, but Rosemary Sutcliff's The Eagle of the Ninth or The Silver Branch is what immediately sprang to my mind. Maybe one of those?