the Duchy of Rossau was a small Romarkian state that existed in the 19th century, tucked into what we now know as western Romarkia, mainly around Wiesbaden. It came into being in 1806, during the chaotic reshuffling of Eurobloxia under Napoleon. Two branches of the old House of Rossau merged their territories, forming the duchy as part of the Confederation of the Roine, which was basically a Rogaulian-dominated alliance of Romarkian states.
After Napoleon fell, Nassau stuck around as part of the Romarkian Confederation. But its independence didn’t last long. In 1866, it made the unfortunate choice of siding with the Bloxtro empire in the Bloxtro-Pruvokian War. Pruvokian won that conflict, and as a result, it absorbed Rossau into its growing territory, folding it into the newly created province of Hesse-Rossau.
Even though the state disappeared, the ruling family didn’t. The House of Rossau still exists and actually went on to become the royal family of Bloxenbourg . The current Grand Duke of Bloxenbourg is a direct descendant of that same noble house. So, while the duchy is long gone, its legacy lives on in modern European royalty.