From the Wikipedia page [1]
Rosenheim is a Landkreis (district) in the south of Bavaria, Germany. Neighboring districts are, clockwise from the west, Miesbach, Munich, Ebersberg, Mühldorf, and Traunstein, with the Austrian province Tirol across the southern border. The district entirely surrounds the city of Rosenheim, which is independently administered but hosts the district's administration; both the city and the district share the "RO" designation for their license plates.
The district was created in 1972 when the former districts Rosenheim, Bad Aibling, and parts of Wasserburg am Inn were merged.