Near the end of 1951 he moved from East to West Germany, enrolling at the University of Münster, studying botany, zoology, physics and physiological chemistry.

Rohde undertook research for his PhD in 1954,[2] under the supervision of Berhard Rensch, a notable German zoologist;[3] his thesis was on the behaviour and physiology of Paramecium.

[2] From 1957 to 1959, he did scientific work at ASTA-Werke, Brackwede/Westfalen (pharmaceutical industry) on the development of new tests for screening anthelminthic drugs (filariasis, hookworms, cysticercus).

From 1960 to 1967, Rohde was a lecturer at the University of Malaya, Kuala Lumpur, conducting work on the taxonomy, life cycles and fine structure of trematodes and monogeneans and supervising BSc.

and PhD candidates in these fields, and, jointly with Tim Littlewood at the Natural History Museum London, Nikki Watson, UNE and others, studied the phylogeny of Platyhelminthes, using ultrastructure, life cycle and DNA data.

His scientific contributions are on the following topics: Rohde was the first who supplied quantitative evidence for the enormous species diversity of marine parasites in tropical (coral reef) waters, and for differences in latitudinal gradients between endo- and ectoparasites.

He has cooperated with Dietrich Stauffer, a theoretical physicist, in using mathematical models to investigate latitudinal gradients in species diversity and niche width.