There are 9 US Post Offices in Rosebud County serving a total of 9,978 residents equating to 1,109 residents per post office. It's estimated that approximately 15,926 packages are handled across the 9 county post offices annually. Rosebud County is a county located in the U.S. state of Montana. Rosebud County was established 11 February 1901, and has Montana vehicle license plate prefix 29. As of the 2010 census, the population was 9,233. Its county seat is Forsyth."