In Roger's time there weren't even Yonkou, at least it has never been mentioned that the 4 original Yonkou had predecessors.
What Chinjao meant by that is simple: Luffy wants to become the Pirate King for which he need to find the OP, the Yonkou also aim for the OP, so he needs to beat them. The admirals then want to avoid anyone finding the OP, so they too will stand in Luffy's way, so he will have to likewise beat them. That's it, that doesn't mean though that Roger had to do the exactly same. Of course he head butted with the Marines and other pirates more than once, but there is nothing that indicates there were already people called Yonkou or that the marines stood in the way of pirates because of their search for OP (which, as far as we know, only became (widely) know after Roger's speech).