He was born in Kampen. As a student he began to write learned articles on homosexual topics following the lead of Magnus Hirschfeld. With long essays on androginy and the history of persecutions of sodomites in 18-century Holland, he opened new terrain for gay studies. He was convinced by the theory of intermediary sexes. He was the first to hold sex surveys among his fellow students, and his statistic were no much different from those of today.

Because of his views he was regularly attacked by scholars and politicians, but he always riposted very firmly. For the Christian-Socialist Rein-leven (Pure Life) group he defended the purity of gay sex in a loving relationship, but no one supported him, not even Aletrino.

The rejection of his dissertation by the Faculty of Medicine of the University of Amsterdam may have been influenced by his staunch criticism of one of his professors. The official reasons were that the book was written in German and included offensive imagery and genealogies of sexual perversion in royal families.

After this setback, von Römer retreated from sexual science. In 1910 he joined as a natural scientist an expedition into the inland of New Guinea, where he discovered unknown plants, some of which received his name. Soon afterwards, he emigrated to the Dutch East Indies, where he married and fathered two sons. After Indonesia's independence he stayed in the country, where he died.

His papers are in the State Archives in The Hague; they contained a sealed package that was opened in January 2000, which included a booklet of poetry (c.1894) about his love for a young man who died early, and other material relating to his sex studies.