Interesting addendum to this that I wasn't expecting: in the English version of Days, whenever Roxas talks about Sora, he's always clearly framed as a person. "Who is Sora," "I don't even know a Sora," etc.
In Japanese, he initially asks about who Sora is, but then switches to asking what Sora is. And it seems to happen not too long after Xemnas describes Sora as "the connection" between him and Xion.
He proceeds to wonder to himself what Sora is, and who exactly that makes him, before going to ask Axel about it. And during that conversation with Axel, he doesn't say "I don't even know a Sora," he instead just repeats the question of "but what even is Sora?"
Which I think adds an extra nuance to the narrative that gets lost in the official translation. Roxas instinctively thinks of Sora as a person, because why wouldn't he, but none of the answers he gets about him frames him as such. So, perhaps subconsciously, he starts seeing Sora less as a person and more of a mystery, this obstacle to his and Xion's lives that he can't seem to get answers about.
And normally, you'd think Roxas wouldn't fall into this trap, right? He's always been the most adamant about defending Xion's personhood, shouting at people when she's referred to as a puppet or an "it." His whole storyline is about asserting himself in the face of nearly everyone he knows dehumanizing him and trying to take away his autonomy.
Plus, he has Sora's memories! If he remembers things that Sora's done, and things that Sora's felt, how could he not see him as a person?
But I think that's a testament to how insidious the Organization's manipulation is. Roxas and his best friend are discriminated against, they're "othered" in a way that's unfair and it makes him justifiably ticked off. But that's the thing: he knows Xion, he cares about her, and of course he knows himself. He remembers things about Sora, but he doesn't really understand him - we never see him processing the memories he has very well.
So it becomes very easy for Sora to be presented as the "other." He doesn't stand up for Sora's personhood because he hasn't seen it, and frankly, he has bigger things in his home life to care about than whether some random guy he knows random things about is being treated well. Sora, reportedly, is half the reason he has so many problems anyway, and at this point in his life he just wants someone to blame.
It doesn't matter that Sora wasn't personally responsible for anything that happened to Roxas. He doesn't know what Sora did or didn't do when it comes to him and Xion, but everyone's telling him he's responsible, he's the connection, he's the reason everything is happening to him. And so, Roxas's anger is directed at an innocent person, someone who's really not much more privileged than he is, instead of solely at his oppressors.
Honestly, the way Roxas views Sora over time deserves a post all on its own, because it's not even necessarily as straightforward as "and then he saw Sora exactly for who he is once they joined together for a while and he got over his resentment." It's more like, his resentment turned into genuine respect, and then into this weird, resigned hero-worship for a bit, before they seemed to get on equal terms towards the end of KH3.
But my point is, Roxas plays a very interesting role in this pattern of Sora being dehumanized, because he ends up contributing to it for completely different reasons than everyone else, and it's not even on purpose. DiZ and the Organization see Sora as a tool, Namine and especially Riku care more about waking him up than how he'd feel about their methods.
To Roxas, Sora is the reason he lost everything. Sora is "what it was all for," which starts as something he hates, and becomes something that gives him a certain degree of comfort.
Because Sora will be the one to figure it all out, right? He can depend on Sora, just like everybody else, because that's what Sora's here for. He's a good guy, he'll find a way to make things right again.
He ends up being correct, but man. At what cost