Roslyn Heights is both a hamlet and census-designated place in Nassau County, New York, United States. It is considered part of the Greater Roslyn area, which is anchored by the Village of Roslyn. The population was 6,577 at the 2010 census.Roslyn Heights is in the eastern part of the Town of North Hempstead at exit 37 on the Long Island Expressway. The Zip Code for Roslyn Heights is 11577.