William Roxburgh Jr was one of the sons of William Roxburgh, Superintendent of the Calcutta Botanic Gardens, and became his assistant. He is the 'Roxburgh, junior' cited by William Roxburgh in his Flora Indica as the author of the name Flemingia prostrata and the collector of a number of other new species.

Appointed Assistant to the Superintendent of the Calcutta Botanic Gardens in 1799, Roxburgh Jr spent much time over the following years collecting plants in the Rajmahal Hills (1800), Chittagong (1801-1803) and Bengal (particularly in the Sundarbans, 1802). He then proceeded from Calcutta to Penang, the Moluccas and Sumatra, where he spent 1803-1804, returning to work with his father in Calcutta in 1805. It is thought that he died sometime within the next year, after a spell of cold weather.

Sources:
I.H. Burkill, 1927, "Botanical Collectors, Collections and Collecting Places in the Malay Peninsula", Gardens' Bulletin, Straits Settlements, 4(4-5): 131
R. Desmond, 2004, "Roxburgh, William (1751-1815)", Oxford Dictionary of National Biography, online edn:
www.oxforddnb.com/view/article/24233, accessed 12 April 2011
D. Prain, 1919, Journal of Botany, 57: 30-32
M.J. van Steenis Kruseman, "Cyclopedia of Collectors", Flora Malesiana, online edn:
www.nationaalherbarium.nl/FMCollectors/R/RoxburghJrW.htm, accessed 20 March 2012.