There are 6 US Post Offices in Roscommon County serving a total of 27,105 residents equating to 4,518 residents per post office. It's estimated that approximately 43,263 packages are handled across the 6 county post offices annually. Roscommon County is a county located in the U.S. state of Michigan. As of the 2010 census, the population was 24,449. The county seat is Roscommon. The county was founded in 1840 and organized in 1875. Both the county and county seat are commonly referred to by locals as \"Rosco\"."