One of the questions that has been ringing in my head is that what has happened to Rosa in AC Brotherhood? Was Venice attack by the Borgia?

3919986 Unfortunately it's a case of Actor Existence Failure. Her VA died in between II and Brotherhood, so she was written out.

I believe there is mention of her in the Brotherhood novel, though.

3920007 Oh I see.

http://assassinscreed.wikia.com/wiki/Rosa

3920964 Ah I see.