[Roger's Devil Fruit] He would be possible to be previous owner of darkness, or gum, or others. I think he previous owner of darkness or gum, because he very strong to taken down a lot of enemies. He would like act like Luffy's beginning, if he previous owner of gum. We will know, after luffy become pirate king. We will see Roger arc later, I'm not sure. And he also enemies with whitebeard, honestly he good pirate king. We should see his past, and how he know about pirate. Maybe someone told Roger what pirate being, and freedom. And Roger should escape death with his own devil fruit, if he has Darkness. I believe Roger's devil fruit mostly like darkness. [Roger's Ultimate Plan] WhiteBeard said "It's not you" "The man Roger waiting for..." "at the very least, Teach" "it's definitely not you." "Just like those are those who carry on Roger's will..." "I'm sure someone will appear to carry on Ace's will, someday." "Even if you extinguish his boodline, there's no way that their flame will ever burn out." "It has been passed down since ancient times." "And in the future..." "Someday..." "Someone will appear, carrying the history of those decades on his back," "and challenge this whole world to a fight." "Sengoku." "You guys in the World Governament..." "all fear that immense battle engulfing the whole world..." "that will eventually come." "I don't care myself..." "but as soon as someone finds that great treasure..." "the entire world will be turned upside down." "And someone will find it." "That day will definitely come sooner or later..." "One Piece" "DOES EXIST!" That what whitebeard talk about one piece. I think, he believe luffy will find treasure. If he tell Sengoku, World Governament might target to Luffy. Roger's plan should be sucessful, and Luffy will carrying on Roger's will.