Thread:AlexanderImAlsoGr8/@comment-27020676-20200311112358/@comment-38474342-20200311173231

AnEvildoer wrote: He said that somewhere in a Q&A in the first volumes of the manga, from what I remember.

And with the Monkey family it's more of a Japanese culture issue. Japanese people usually use their surnames first and the author is Japanese, so he does it that way for those characters too, not only pirates. But beside Japan you can put their surnames second, it's okay and still correct. I'm sorry, I just do not want to leave any room for doubt. But unless there is evidence showing that Zoro's name can be typed "Zoro Roronoa", then there is no reason for it to be so, since no source provides his name in that style, be it from the manga, anime, fandoms, Wikipedia or anything else, really

And you're probably right about  it being a part of Japanese culture, so its safe to assume that Zoro's name is treated the exact same way and that his surname (Roronoa) is used first, before his given name (Zoro)