[spoiler]Re Cassandra's question about Roxanne's destruction, I believe it was Barnabas who told her brother about her and what he had to do. So, this would be a new thing that happened after they went back in time. So, the first time she wasn't destroyed, and now she is.[/spoiler]
However, I've always been bothered about how she originally became a vampire, seeing that Barnabas wasn't released from the coffin that time. The children also mentioned remembering attacks like that when they found the body in the woods. So, we have to guess that another vampire was on the scene originally. But, then where is it now?!!