The x makes it look ugly and silly to me. I've never seen surname Roux - I just think of making gravy. I have only seen a silent x at the end of a name or word, never in the middle, so it's confusing.
I think Ruzanne or Rouzanne would not be bad, though. It reminds me of
Roseanne (and
Ruzha,
Ružena).
- mirfak