From 1987 until 1998, Rossmann served as a member of the State Parliament of Schleswig-Holstein. In this capacity, he was his parliamentary group’s spokesperson for education policy from 1988 until 1996.
Rossmann became a member of the Bundestag in the 1998 German federal election, representing the Pinneberg district.[2] Throughout his time in parliament, he was a member of the Committee on Education, Research and Technology Assessment.[3]
In July 2020, Rossmann announced that he would not stand in the 2021 federal elections but instead resign from active politics by the end of the parliamentary term.[4]