[1] Rosenmöller was born into a Catholic family in Den Helder in 1956; his father was CEO of Vroom & Dreesmann.

In 1985, he became a member of the board of the Transportation branch of the Federation of Dutch Trade Unions (FNV) in Rotterdam.

In 1993 he was candidate party leader together with Leoni Sipkes [nl], but they lost the internal elections to Mohamed Rabbae and Ina Brouwer.

In the hardened political climate after the murder of Fortuyn, serious threats against Rosenmöller's life and family were made.

As member of parliament, Rosenmöller showed interest in the situation of the Netherlands Antilles and social participation of immigrants.

During the annual General Political Debate in October 2024, he introduced a motion calling the planned declaration of an asylum crisis by the Schoof cabinet through emergency legislation undesirable, and he urged for an alternative approach.

Minister of Asylum and Migration Marjolein Faber responded that she remained intent on using emergency powers.

[5][6] In 2003, after leaving politics, Rosenmöller became a television presenter for the Interkerkelijke Omroep Nederland (IKON), which was an ecumenical broadcasting organisation.