Roger, besides being Pirate King, was well known for the wealth he had accumulated. Prior to his death, he's questioned as to the whereabouts of his wealth⁽¹⁾ where he proceeds to gives a rather cryptic response, and it is this wealth that he accumulated that is the One Piece...
I have to get to work so I'll keep it short.
Here is a recap on what we know this far:
Who can hear the "voices"?
Who can communicate with these voices?
What does this mean?
So the mystery deepends. Looks like the past and future pirate...