Rosethorn Hall is the most expensive house you can purchase in the game. The house is located in NE Skingrad, on the west corner of the eastern arterial road connecting the North and South sections of the city.
The house is bought from Shum gro-Yarug, who can be found at Castle Skingrad in the day-time, or in the Inn. If you're having trouble finding him, talk to someone in Castle Skingrad about buying a house, they'll direct you to him with a map marker so you can easily find him. To be able to purchase this house, you need 25,000 gold, a fame of 15, and have your disposition with Shum at 70 or above. Buying this house will kick out its former tenant.
The house has a basement and three stories, and the master bedroom is on the top floor. After buying all of the furnishings, the house will be decorated and have many chests and display cases to place items in. There is also an exterior balcony on the second floor.
Buying this house also allows you to begin two mini-quests.