The Root of Mystery is a legendary spell book, containing the art of long forgotten magics. You found clues about where this book might be. Based on your information, the book is in a hidden library, somewhere deep inside the Roots Forest. The forest is sacred and has fearsome guardians that looks like trees, but they can move pretty fast. If they think you are a threat, they will eliminate you. So be careful and don't cause any damage if it's possible, or suffer the consequences. I think you can deal with one or two guardians, but more of them will be problematic. Good luck!
Walkthrough for Roots Forest Mystery