The following history of Rosanky is taken from The New Handbook of Texas published by The Texas State Historical Association.
Rosanky, on Farm Road 535 11 miles south of Bastrop in southern Bastrop County, is named for Ed Rosanky, member of a pioneer Prussian family who settled in the area in 1854. The loosely organized community that grew up in the area was first known as "Snake Prairie." A Snake Prairie school was established in 1868 and a post office in 1871 with Mrs. S. C. Hutchinson as postmistress.
With the coming of the railroad in the early 1890s, Ed Rosanky donated land for a station and built a store. The post office, which had been renamed "Eagle Branch" in 1884 and discontinued between 1889 and 1891, was renamed "Rosanky" in 1893. In 1896 Rosanky had a population of 100, three churches, three general stores (two containing saloons), a corn mill and gin, a cotton gin, and a blacksmith shop. By 1909 the settlement was a "thrifty little town" of 250, according to one contemporary newspaper.
The population was reported at 250 during the 1920s, when the Rosanky area became an oil-testing site. In 1933 the community reported two schools: a 10-grade, 50-pupil school and the Ford school for black children. By that time the population had dropped to 190, where it remained through the late 1960s, when it took a slight upward swing. The population was estimated at 210 from 1970 to 1990, and 250 in 2000. The community, settled and developed largely by people of German extraction, has served as a trading point for surrounding livestock-raising operations. In the mid-1980s many of its residents commuted to jobs in Bastrop, Smithville and Austin.
Bastrop Advertiser, Historical Edition, August 29, 1935. WPA Texas Historical Records Survey, Inventory of the County Archives of Texas (MS, Dolph Briscoe Center for American History, University of Texas at Austin).