Please do not renounce your words about Roxas (and Xion), even if there is no evidence what role they will play in Post-KH3.
It still seems to me that Roxas is still an important character, at least because he is nobody Sora and he has two keyblade.
But yes, he is a favorite of fans, for the same reason Nomura returned Axel.
Personally, I have several plot developments related to Roxas in future games.
First, I think Roxas will try to find its place in the world, spotting filovskie questions about yourself. In a game like KH2 and Days, the topic was raised more than once that “Not everything can be as it always is” and, first of all, it referred to the end of the prologue of KH2 and Days, but given the current theme of maturity from the title to the title of Nomura, I can believe that this topic may again be touched upon and in particular by Roxas. Perhaps he will start thinking about sitting on the tower and eating ice cream, is that the thing he wants to do all his life? After all that happened to him and his friends, they are no longer the same people.
Axel / Lea wants to become a keyblade master. And Roxas and Xion are not the same cute guys who needed to eat Ice cream to be happy. They had to endure too many bad things.
It’s also because Roxas matures, and people become more difficult with age. I can quite believe that Lea will try to keep their trio, however, he and Roxas will finally understand that they should give up and let them temporarily. I was inspired by such an outcome from cartoons How to Train Your Dragon 3 and Ralph 2, but I just think that such an outcome takes place in this KH.
Also, as you said, the main test of Roxas will be the acceptance of what he is special, as well as getting rid of trying to play someone else’s role and finally become one’s own person as he wanted.
Of course, these are just my thoughts. If this does not happen, I let it sadly, but accept it. But in any case, thanks for your post, you threw me more thoughts about the future of Roxas.))