Profile

“You don’t know about it? Okay, I’ll explain it to you.”

She is a beautiful warrior with a sharp tongue and a deadly sword. She will teach Dart much about the art of Dragoon warfare and fights beside him in many battles. There is a well-guarded mystique about her.
Game manual

Rose is the first character to make an appearance after the game’s opening video, and, after Lavitz and Shana, the third playable character to join Dart on his journey.

A woman with long black hair, fair skin, red lips, wearing a purple-coloured piece of armour with gold ornaments. Her gaze is serious, her mouth unsmiling.Though she has saved his life twice by that point and has agreed to accompany the group on their quest to slay a Dragon for the sake of the kingdom, she remains a mystery to her fellow travellers. She offers no information on her past, hometown or family, and they do not (or dare not) ask. In battle, Rose wields a rapier, and as the holder of the Dark Dragoon Spirit, her element is darkness.

Another commonly cited and presumably official profile (source unconfirmed) of Rose offers far better wording than Prima’s Official Strategy Guide, though they are strikingly similar in part:

The mysterious Rose is a warrior who fights alongside Dart. Nimble with a sword, she slices through the world with a knowledge far greater than most. Her mystery and allure enchant all who meet her, yet she remains alone.

According to the official Japanese guidebook, Rose appears to be about 26 years old and 170 cm tall (5’6”).

Role

Rose initially acts as a guide and mentor to Dart, the party and the player. By activating the dormant Dragoon Spirit in Dart, it is her who, at first glance, initiates the chain of events that sends them their journey. She provides him with knowledge of the Dragoons, ancient weapons and creatures thought to be extinct — knowledge that proves to be crucial as they find themselves caught in a plot of a scope far greater than they can imagine, starting with Shana’s prior abduction. Rose further teaches Dart how to wield his power, that is to say, how to fight as a Dragoon, and warns him of its dangers later on.

Lavitz: Why do you know about such things? You know too much about things nobody could know.
Rose: It’s better than ignorance, isn’t it?
Lavitz: That’s true, but yours is not mere knowledge. It’s a story in a legend that has been lost.
Disc 1: Hoax