Rose Hill is a city in Mahaska County, Iowa, United States. The population was 157 at the time of the 2020 census. According to the United Stat…Rose Hill is a city in Mahaska County, Iowa, United States. The population was 157 at the time of the 2020 census. According to the United States Census Bureau, the city has a total area of 0.14 square miles, all of it land.