No. It hasn't been said in the games or in real life, but the information we have been given is roughly thus:
Roxas can wield Keyblades because he holds part of Sora within himself (even though he is part of Sora) and Sora is alive but sleeping at the time. If Sora was awake while Roxas was 'alive', Roxas would most likely lose his Keyblade-Wielding abilities, because Sora would be making use of them.
He wields the Oathkeeper and Oblivion keyblades because of A) their representation of Sora's relationship with Kairi and Riku and B) because one reperesents Light and one represents Dark, and Nobodies are kind of in the middle, yet also completely off from both at the same time.
And cos' Nomura just wanted someone to dual-wield Keyblades because dual-wielding is always cool, and it is only made more awesome by the fact that it is done with Keyblades