From 1443 to 1453, under the reign of Christian I of Denmark, he also served as Royal Chancellor (Kongens Kansler).
Rosengaard belonged to a branch of the Rügen noble family Schlaweke that had settled on Zealand.
He was the son of Tetz Rosengaard til Kværkeby (died c.1420) and Tale Jensdatter Qvitzow.
[2] Many members of the Danish branch of the family were high-ranking clergymen or government officials.
He was responsible for the administration of the bishop's fief Selsø for a time, and was also here involved in a dispute with his neighbor, Peder Bille of Svanholm.