May 13th. At least, That's what I want it to be, since he seemed to bloom into a very powerful and awesome flower, then he wilted into Sora's summer heat 의해 the end of July. It just seems right to me. ^_^
And why does everything Roxas related have to be Sora's? He is HIS OWN PERSON, made of BOTH Ven and Sora! Roxas isn't a retard copy of that brat Sora. And jr, that made no sense at all. 의해 the way, none of 당신 know Sora's birthday, they don't have them. This is just what i woul uppose it being. If Roxas was the same as Sora, he would've killed Hayner, Pence and Olette thinking they were such horrible people.
Im pretty sure your looking for a 날짜 but there is no official date. The only lead there is is that he was born when Sora sacrificed himself to release kairi's 심장 back in KH1.