Ok every body thinks that the glowing eyed unknown is roxas but i have some stuff here that you should read and if you still think it is roxas then thats your beliefs but i think it is a organization 13 heartless that walks through that rock. Here is that information:

This glowing eye unknown is a very mysterious character. The GEU is first seen in the Deep Dive trailer, as he walked through a rock, like a ghost like creature. From seeing this, many believe the he is not a "mere shell", but the heart of a character. After seeing the bottem picture, many believe that the GEU could be a heartless himself, due to the fact he has the glowing eye and the heartless symbol that appears.

The glowing eyed unknown also has long boots that are pointed with his pants tucked in. The duel wielding unknown however, has a shoe buckle and a rounded front and his pants are not tucked in. This clears out the rumor that the dual wielding unknown and the glowing eyed unknown are the same.

Now, the big thing. It was said to the glowing eyed unknown, "He looks just like you." It is assumed that this is a reference to Sora, based on the Enigmatic scene in Kingdom Hearts: Final Mix. BUT, who knows, it may not be a reference to Sora. The person who said "He looks just like you", was another unknown who is just seen sitting on a mysterious beach.

The screenshots above and below are of the sitting unknown, as he tells the glowing eyed unknown, "He looks just like you."