so at the end of this clip,was that roxas in the black hood?!

Why do you think that?

Also, who is the brown-hooded guy with Riku in Destiny Islands?

I would have liked it more if I could hear it. Too much background noise. =[ ​

I beleive that is Xehanort, mainly because that was the outfit he wore before he took over Riku's soul. My only guess is that Riku and Xehanort have met before the events of kindom hearts 1, planting dark thoughts into Riku's mind.

I'll spoil it for you. It's

Spoiler

Riku in his Organisation coat, the version (as in, character model) shown at the end of RE:Chain of Memories. In this case, this version of Riku is merely a digital avatar used by the Jiminy's Journal to communicate with the King and Data!Sora.

Org!Roxas does appear in coded, but as a boss fight at the end of the game who's similar in nature to Riku in 358/2 Days.

Now that I actually take a good long look at this game it looks amaaaaazing. I seriously need to get it, from the looks of things it has the potential to be my second favorite KH ever.

wow. We're looking at a Christmas release.