House Rosenberg of Arcastle is a Great House of Thaelia, ruling over the kingdom of Ardenfrom their seat in Arcastle, recently attacked by House MacPhaiden of Othiria It is the founding family of the kingdom of Arden, and has rules for over 800 years. The head of the house if lord Maximus von Rosenberg.

Sigfrid von Rosenberg rebelled against Orlenerule in 318 from the city of Rosen. Through good planning, high moral and discipline and good diplomacy, Sigfrid secured the southern coast of the Inner Blue Sea for himself, including Arcastle. Shortly after, House Blumenthal rebelled and won independence. House Blumenthal and House Rosenberg married, merging their kingdoms into Arden, and the capital was moved to Arcastle.