[5] Von Rohr was an immigrant to Denmark, and in 1757 was appointed as municipal buildings inspector and government land surveyor of the Danish West Indies, now known as the United States Virgin Islands.
Von Rohr started a botanic garden in Christiansted on the island of St. Croix, corresponding with noted natural history scientists back in Denmark and in Europe.
[6] In the 1790s Denmark considered abolishing the Atlantic slave trade, a measure expected to bring down the flourishing sugarcane plantations of the Danish West Indies.
Von Rohr, who by this time had acquired considerable administrative experience of the colony, was asked to investigate the feasibility of establishing plantation agriculture in the vicinity of the old Danish slaving forts of Guinea on the West African coast.
Von Rohr packed and sent ahead to Fort Christiansborg his surveying instruments and library, a catalogue of titles reflecting his colonial involvement.