Rose is a female warrior who you meet early in the game. She's been a Dragoon the longest, so she's forced to teach the others what to do. And she's good at it too. Her skills rock, and her first spell allows her to steal HP from the enemy (good since you won't get the W. Silver Spirit for some time).
You first meet Rose in the beginning, when she sees Feyrebrand in the forest. She runs into it, only to end up saving Dart and telling him of his village burning. Later, she helps Dart to transform into a Dragoon to defeat Kongol. Then she and her awesome powers joins the team.
As the game goes on, Rose becomes more and more mysterious. She never talks about herself, or answers questions that the others have. On the Black Ship, she is even confused for the Black Monster that goes around killing the Moon Child every 108 years.
When she and Dart fall off the ship, and she's watching over him in a cave, you learn about her past. In a vision, she remembers her fighting in the Dragon Campaign 11,000 years ago, and the death of her friends. Rose reflects on how much Dart reminds her of her lover, Zieg, who was turned to stone on the sword of the Wingly Emperor.
Near the end of Disk 3, her past comes out. She find out that Zieg is alive, and is the one trying to destroy the world. Even more amazing, he turns out to be Dart's father. He also reveals that the Moon Child is actually there to destroy the world, not save it, and that Rose is the Black Monster--using that identity to kill the child, and all who have contact with it so they don't go mad. Zieg kidnaps Shana (the Moon Child), and attempts to destroy the world.
When you finally catch Zieg, you learn that he was possessed by Wingly Emperor Melbu Frahma. You free him, and then defeat Melbu, who becomes the God of Destruction. In order to kill him, Rose and Zieg fly to the heart of the beast as the others escape. In the end, they both die valiantly, ensuring the future of the world.
Intelligent, well what else would you be after that long a life?
One of the fastest Dragoons.
Her addition, More and More, can give you a full level on your Spirit Gage if done successfully. It isn't too hard to do either.