J.A. Roorda Smit was awarded a doctoral degree in mathematics and the natural sciences in the Netherlands. During a visit to the Netherlands in 1875 President T.F. Burgers of the South African Republic (Transvaal) engaged him and Dr E.J.P. Jorissen to teach at the gymnasium (high school) to be established in Pretoria. Roorda Smit planned to leave for the Transvaal on 20 November. In a later announcement of his appointment (De Volksstem, 5 February 1876) he is described as a very able and promising young person whose endearing personality would earn him many friends. He was also supposed to function as government assayer of agricultural soils.
Roorda Smit arrived in Natal. On his journey to the Transvaal he found a plant fossil and, along the Drakensberg, some petrified wood. By the end of March 1876 he had already undertaken several short excursions in the vicinity of Pretoria to collect samples of building stone and study the local geology. [His knowledge of geology seems suspect, as he claimed to have discovered a fossil fern in the sandstones at Daspoort, Pretoria - perhaps a set of branching dendrites]. He had brought chemical apparatus and chemicals with him from Europe, which he asked the government to buy so that it could be used at the gymnasium to teach chemistry and mineralogy. As far as is known the government did not respond, even though he conducted some chemical analyses for government officials during 1876. The gymnasium opened towards the end of June with only five pupils, but this number had doubled by the end of September.
An important initiative by Roorda Smit was to establish a museum and library to serve the gymnasium. A public request for specimens and books was published in the local press in September 1876. Early donations acknowledged at that time included a collection of 120 minerals by J. Preller, some maps, and a number of animal heads. Roorda Smit envisaged that the museum would serve mainly the study of geology (rocks, minerals and fossils), zoology (skeletons, stuffed animals, specimens preserved in spirits), botany (an herbarium), the physical sciences (scientific and mathematical instruments), and anthropology (cultural artifacts), while the library would cover both science and literature. The opening of the museum took place on 25 September, in the presence of the State President and other high officials. The collection was housed in the residence of Dr Jorissen, but was curated by Roorda Smit and appears to have been accessible by appointment only. Donations were acknowledged in the press under the title "Staatsmuseum der Hoogeschool te Pretoria" (State Museum of the High School at Pretoria), implying official government support for the venture.
On 12 April 1877 the Transvaal was annexed by the British without opposition. The next day Roorda Smit wrote to Sir Theophilus Shepstone declaring himself willing to serve as teacher under the new administration. However, in July that year the gymnasium was closed and the laboratory, museum and library (then containing about 1000 volumes) were taken over by the government. It is not clear what became of the museum collections. Though Roorda Smit's efforts were short-lived they constitute a significant first attempt at science education in the Transvaal.
The British administration appears to have offered him an alternative position, which he declined. He may have left for Europe at this time, but in April 1878 was again (or still) in South Africa, visiting the diamond fields around Kimberley. This visit led to a paper, "Les mines de diamants de l'Afrique australe" (The diamond mines of South Africa), published in the Archives Neerlandaises des Sciences Exactes et Naturelles (1878). The paper contained a description of the diamond fields and dealt with the geology of the region. A few years later a paper by him on "De bodemgesteldheid in de Transvaal" (Soil conditions in the Transvaal) appeared in the Tijdschrift van het Koninklijk Nederlandsch Aardrijkskundig Genootschap (1882). Some other publications by him dealt with other aspects of South Africa: A pamphlet on the Zulus (not dated) which refers to the Anglo-Zulu War of 1879; a lengthy paper on the Khoi entitled "Contributions a la connaissance de la race hottentote" (Archives Neerlandaises..., 1880); and Het goed recht der Transvaalsche Boeren (Utrecht, 1881, 108p), a book in which he defended the South African Republic against British imperialism.
From about 1883/4 to 1888 Roorda Smit was professor of physiology at the University of Cordoba, Argentina. During this period he was a member of the Honorable Academy of the School of Medicine and during 1885-1886 served on the Superior Council of the university. In October 1889 he was appointed as Dutch vice-consul in Cordoba. Many years later, in 1919, he became co-founder of the Argentine-Dutch Chamber of Commerce in Buenos Aires.
After leaving South Africa Roorda Smit published pamphlets in Utrecht, The Netherlands, on his research on the Bischof filter (1882) and the treatment of cholera with calomel (1888), as well as papers on the cholera in Cordoba (Nedelands Tijdschrift voor Geneeskunde, 1887) and the causes of mortality and morbidity (Archives Neerlandaises..., 1897).