ONE PIECE GOLDAfter 818 i’ve seen many people wondering(myself included) what the use of Oden Kozuki was on Roger’s crew, considering that Roger had the ability to hear the Voice of all Things. If Roger could understand the Poneglyphs with this ability, what was the purpose of having someone that could read the ancient language?
Well, i think that Oden was in fact the man that created the Rio Poneglyph on Raftel!
Let’s take a look at what we know about this character so far:
He’s one of the few people that have been confirmed to be on Roger’s crew, but more importantly, he’s been confirmed to have actually set foot on Raftel! Then Oda continues to reveal that his clan was the one that created Poneglyphs and that this ability unfortunately died with him before he could pass on his knowledge to Momo.
I don’t think it’s a coincedence that the last man who was able to create a poneglyph was on Roger’s crew.
Oda didn’t let Roger have this man and this specific ability with him for no reason, cus he’s Oda!
As we all know from the Poneglyph on Skypiea, Roger gathered its information and took that information to Raftel. Hence, Robin said that the purspose of that Poneglyph had been fulfilled and no longer needed to be protected. So we know that Roger gathered all the pieces of the puzzle and put that puzzle together at Raftel.
When they reached Raftel and learned the whole truth, for some reason Roger could not act upon it. Whether it was his illness or some other reason we don’t know, but he could not act. That’s why he decided to leave the information, knowing that some day someone with the will and capability to act on it will appear.
Now, of course, Roger wasn’t just gonna write this combined knowledge about the history of the world on a piece of paper. He wanted it to be found by someone who had the knowledge and Will to find out the truth.
Also, he didn’t want this information to be able to perish. Now what a coincedence that the one man in the entire world who could create an indesctructible poneglyph was with him on Raftel 
.
So Oden Kozuki used all information that Roger had gathered to create the Poneglyph that tells it all: the
Rio Poneglyph. Creating this poneglyph might also be (part of) the reason why Roger had his “timeskip” after reaching Raftel!
That’s it, hope you guys think it makes sense and enjoyed it!
*Theory by Arasys