This is, unfortunately, not a new book that she has written (yes, I’m disappointed too). Rouge is the French translation of Fire, her companion book to Graceling. Rouge meaning red in French (not the best translation for fire imo but maybe it works). If you are actually interested in the French book, check out Hachette’s website here.
If not, Fire is in my review pile so there will be a review up soon. Until then, here is the book trailer.
Edit: I have since reviewed Fire, you can read my review here.