I want to share a crazy theory I came up with some time ago. Now as you can read in the title, I believe there is a possibility that Luffy could be Rogers reincarnation. After all, Luffy was born after he died. But other than simply inheriting his spirit, is there maybe an inuniverse explanation how that could be?
We're all aware, that some devil fruits do something similar, yet different. We have the pairs of ice and snow, fire and magma, the ability to turn your body into a blade and into any kind of weapon as well as the weight manipulation which could either go from several kilograms to tons. So with that knowledge in mind, could it be that Roger ate a yet unseen devil fruit that could be able to let him live on, even after his death?
We know of one devil fruit that actually does something like that. Brook's yomi yomi no mi. But since he is still using that power, Roger couldn't have eaten that. But as mentioned above, he could've eaten a fruit that doesn something similar ... so instead of being revived in your old body, maybe he ate a fruit that would revive him in a new body?
Over the course of the series there are many people who noticed similarities between Luffy and Roger. On top of that both of them are among a few amount of people who can hear the voice of all things as well as Zunesha's voice.
That's why I think there is a possibility that this might be a future twist. (alternativly Roger was reincarnated into another body and is still aware of his past as Roger but is hiding that fact from the world, maybe someone we already saw)