This is gonna be a long read so apology for that
Zoro is one of the main characters in the story and it is very common in Shounen for the character aiming to be strongest of his era to end up becoming strongest of all time. I find it very hard to believe that Oda would expand up swordsmanship in One Piece through Zoro's journey, have us follow his path to becoming strongest swordsman in the World and have there be a swordsman in One Piece history superior to Zoro. It would be equivalent of there being a pirate in history of One Piece whose notoriety and status would not be surpassed by Luffy and I don't see that happening.
Where Mihwak stands in comparison to Gol D Roger
Now regarding Mihawk vs Roger, I do think Roger is stronger than Mihawk but I don't think gap between them is humongous and Roger would need an extreme difficulty fight to beat Mihawk. Well for starters I don't even think Gap between an average top tier like Shanks and Roger is big and Roger would defeat Shanks in a high difficulty fight. But there are three top tiers that I have as exceptions among even current top tiers and whose strength nearly rival Roger's and those are Mihawk, Blackbeard and Akainu and Blackbeard may have even surpassed Roger.
I wouldn't discuss Akainu for now but Mihawk particularly I have there after the events of Wano, and how much hype swordsmanship received with fighting style of Pirate King being swordsmanship and the scar on the most durable character in history being due to swordsmanship as well.
Mihawk so far has been portrayed as peak of swordsmanship in One Piece due to his title and him making a permanent black blade and most importantly being ultimate destination of one of the main character whose entire character revolves around combat strength and becoming the strongest swordsman he possibly can be.
Mihawk has a few points in favor when directly compared to Roger like Roger not being able to accomplish feats of swordsmanship good enough for the world to recognize him as strongest swordsman or his era or Roger not making a black blade. But I would still favor Roger due to his Pirate king title and the fact that he was stated to be equal to Whitebeard in his prime.
For the record I had Kaido up there with Mihawk, Blackbeard and Akainu as well but I bumped him down slightly after Wano because it just doesn't make logical sense for Kaido to be weaker in his late 30s considering he is a born freak of nature even more so than Oden and it also doesn't make logical sense for me for Oden to be that close to Mihawk (Mihawk would high diff both Oden and Kaido).
Maybe I am wrong, maybe Kaido did get stronger, maybe Mihawk is significantly weaker than Roger, maybe Mihawk is not stronger than Oden at all, maybe Zoro will never surpass Roger but so far this is how I perceive manga and it makes the most logical sense to me as far as individual strength relation between Roger, Kaido, Mihawk, Oden and EoS Zoro is concerned.
Why becoming Pirate King being harder than becoming WSS is not a valid argument
First of all Mihawk never claimed becoming pirate king is
much harder it is dishonest and no different than someone saying becoming pirate king is only slightly harder, all we know is becoming pirate king is tougher than becoming World's Strongest Swordsman.
But regarding the main argument about Mihawk's statement of
Becoming pirate king is tougher than surpassing Mihawk. Its like no shit becoming Pirate King is harder.
To becoming Pirate King
-You need to have strength required to go through journey around the world and deal with obstacles in the way
-You need to be charismatic enough to have ability to acquire an exceptional crew that a pirate king would
-You need to deal with 4 emperors of the sea and their crews as they are aiming for same goal and one of the emperors have one of the poneglyphs showing the way to final Island where your journey would end
-You would need to deal with Marine Admirals and rest of navy as you are essentially aiming to becoming biggest criminal in the sea.
-You need to journey around the entire world in attempt to find one remote Island
-You need to find someone who can read road poneglyphs
If doing all that is not harder than surpassing just one man than Pirate King title doesn't mean much. Like I don't understand this absurd way of thinking, no one here is claiming that Mihawk has everything it takes to be Pirate King instead just individual strength considering individual strength is literally what his entire character arc revolves around.
Anyways yeah EoS Zoro would defeat Roger in a high difficulty fight
Though like
@Admiral Lee Hung it is anyone's guess at this point. Roger > EoS Zoro would make sense and EoS Zoro > Roger would also make sense