There will be a 10 minute preview of the second Winx Club as confirmed by this article.
Also, this extremely short article says:
"After the success of the first film, return the six fairies most beloved by the girls in a thrilling adventure in 3D.
So does that mean that Roxy won't be there? We can only wait until the ten minute preview to come out and give us some sort of confirmation.
(Also, the picture on the right is Roxy in the Winx Club comics from what I understand. Completely unrelated to the movie.)