Go to Castle Spree near Spree in the Mellow Hills. Proceed down into Dungeons of Spree. Here, you'll find Rose. To get her to come with you, you will need to kill all the raiders and retrieve her luggage.
Proceed through the dungeons, killing enemies, until you get to Rose's Luggage. After you carry it back to Rose, she’ll come out of the room that she’s hiding in and come back to your Tower.