[1] His parents, Bernhard Roßmann (1910–1958) and his wife Hilde, née Wilkens,[3] ran a small drugstore on the outskirts of Hanover in the second generation.

[4] At the age of twelve, he earned his first money by selling pharmacy goods ten per cent cheaper.

[5] At the same age, he also learned from his mother, at his own request, that his biological father was the neighbour, Theodor Kayser (1899-1968), the son of a German manufacturer from Warsaw and the godfather of Rossmann's older brother, Axel.

[1] In the 1980s, Roßmann sold 40 per cent of his company to Hannover Finanz, and its stake went to the drugstore chain of the Dutch Kruidvat Group (former owners: the De Rijcke family), which in turn was taken over in August 2004 by the A.S. Watson Group of the Hong Kong conglomerate Hutchison Whampoa.

After the fall of the "Iron Curtain" in the early 1990s, Roßmann's company expanded into the Eastern European market, where he has operated over 1,000 shops since 2009.