KH (Birth by Sleep)- Vanitus fought Ventus for his body which after he cheated and somehow won by losing, tore out Ventus from his body (not literally, he was taken out but somehow made it to Sora who started the mess from square 1). Sora forgot about after about a month or so. When darkness came to the island, Ventus stained Sora's heart so Sora could use the Keyblade while Ven was sleeping.
KH- When Sora stabbed himself, didn't you notice 8 hearts instead of 7 (seven princess of hearts)? The 8th would have been Ventus because Sora never left the room until after he became a Heartless which is where his heart was.
KH (CoM+Re:CoM)-Sora acted more and more hostile to others the longer he stayed but that was also the same time Roxas was unconscious in Org. XIII.
KH (358/2 Days)- Roxas acted kind to Xion and Axel and cried when Xion died but proof that Axel also thinks Roxas isn't Sora's Nobody is in his journal which I quote, "I just don't see it." Meaning that Nobodies who look human are supposed to match their original selves by look.
KH (2)-Roxas laughed and showed rage(emotions)