Rosé is from the city of Lior in a remote region of the East. She was a devout follower of Cornello's teachings because she felt that he would use his powers to bring her boyfriend, Kain, back to life. Instead, Cornello created a talking parrot chimera to mimic Kain's voice. When Rosé discovered this, he locked her in the room with it, using the incomplete Philosopher's Stone to get it to attack her. Al saved her, and together with Ed, they discredited Cornello.
(Source: Wikipedia)