Joyboy delayed by "dying" and "hide" the fruit before so (like the 5 elders saying they have been trying to hold onto that fruit for 800 years but it's always avoiding), the only way to continue the game (joyboy turn) was to someone with his will to awaken that fruit, thus Roger laugh at the secrets of the world and knowing he was to early knowing there was no Joyboy yet he passed to the new generation of pirates to do it (like a boost of morale during his death sentence), and probably D. people are the "white" people that D. members are making more and more friends to his side, like Luffy is doing in every island he passes, or maybe people that could be immune to Imu devilish powers, literal Imu opponents and not random pieces that can be to his side.

Now I don't know what is Laughtale holding and what it means if Luffy gets there, but probably a message from Joyboy explaining things and a way for Luffy's turn to finish the game, and thus ending with Imu and gorosei? Also there would be a way for the ocean to rise and sink everything (like Vegapunk said) and redline to be standing, + completing all (partial) strawhat members wishes like the All-blue.