Why would he leave his logbook at the end of the Grand Line? Especially when the Rio is there anyway.
Flashback memories are nothing like the sort of logbook memories of say Zeff. One are horrible emotional scars being shown as the point of what needs to resolved in that arc with that character, the other is a one time semi-motive for a lame villain.
I see no Corelation at all.
I don't see how Dreams is connected to "memories".
Perhaps you don't understand what a logbook is. It's a diary, more or less. A captain writes it describing his voyage. To me, a person's memories would be the most valued thing to them, because it reveals all they've learned, and it's the only real thing you can take with you when you die. Gold, ships, possessions and other things are all meaningless when you're dead.
By recording your own personal thoughts and feeling, you give One Piece of YOUR memories, One Piece of your journey in life. One Piece of Life's journey, as told by you.
You're looking too narrowly, Zephos. What good would gold and jewels and ships be to Roger if he couldn't take it with him? What good is anything material in death? And those that covet these things in life are just foolish.
The Rio Poneglyph IS Roger's logbook. I think the conclusion that Robin came to is that the Rio Poneglyph is a collection of everything that was written about the lost history, compiled into one document. Maybe it was carved on the poneglyph stone, but I strongly believe that either Roger or his archaeologist (If he's not Nico Robin's father) wrote the Rio poneglyph. After all, Rio means River in Spanish. Time flows like a river towards a final end; in that sense, all the Poneglyphs flow like a river of knowledge toward a final truth. So, there WAS no Rio poneglyph until Roger reached the end and recorded it.
As for how dreams are connected to memories, that's simple. Memories of the past are what drive people forward to the future. Sanji's memories of Zeff's Sacrifice, Luffy's memory of Shanks' sacrifice, Usopp's memories of his mother praising his father, Chopper's memories of Hiruluk, Robin's memories of Saulo and Olivia's sacrifice, Zoro's memories of Kuina, Franky's memories of Tom, Nami's memories of Belle-Mere's sacrifice. Every Strawhat has a dream for the future, and it's the memories of those that inspired them and encouraged them to live out these dreams that drives them forward.
That's why I believe it's Roger's logbook. Because Roger's treasure, like all of the strawhats, is his memories of the past.
Which leads to a good question: Who inspired Roger?