Rotheram Mill House, also known as Harmony Mills, is a historic home located at Newark, New Castle County, Delaware. The house was built about 1740, as a 1+1⁄2-story, five-bay, gambrel roofed brick dwelling. Before 1775, the roof was raised to a full three-bay second story with a gable roof. It has a two-story rear kitchen wing. It was added to the National Register of Historic Places in 1972.