Rudolph (or Rudolf) F. Roser was a missionary of the Moravian Church who arrived in South Africa in 1848 and was stationed at the Moravian mission at Gnadenthal (later Genadendal) until 1869. He was married to Anna C. Stephan of Zeist, The Netherlands. Roser studied and collected the local flora and in 1855 received a collection of plants from Reverend L.R. Baur*, which he took to Germany with his own collection. He obtained the degree Doctor of Medicine (MD) in 1856, under the supervision of Dr W. von Rapp of T?bingen. His thesis, Naturhistorische und Medicinische Beobachtungen ?ber Gnadenthal in S?d-Afrika (T?bingen, 1856) included a list of plants growing in the neighbourhood of the mission; a list of indigenous trees with their common names, characteristics and uses; a descriptive list of medicinal plants used by the Khoi, with their common names; and references to his medical work at Genadendal. After his return to the Cape Colony he was licensed to practice medicine in November 1862. W.H. Harvey* thanked him for "an interesting series of well dried specimens" from the neighbourhood of Genadendal, in the preface to Volume 1 of the Flora Capensis (1860). Some plant specimens collected by him are in the Compton Herbarium, Cape Town.