Rosedale is an unincorporated community and census-designated place in Baltimore County, Maryland, United States. The population was 19,257 at the 2010 United States Census. The etymology of Rosedale remains uncertain and lacks definitive documentation. However, according to anecdotal evidence, a fourth-grade class in 1950 was instructed to co…Rosedale is an unincorporated community and census-designated place in Baltimore County, Maryland, United States. The population was 19,257 at the 2010 United States Census. The etymology of Rosedale remains uncertain and lacks definitive documentation. However, according to anecdotal evidence, a fourth-grade class in 1950 was instructed to conduct interviews with local residents regarding the history of the Rosedale community. From their interviews, a possible explanation emerged: A young Englishman had a farm on Hamilton Avenue just above Philadelphia Road. His farm had numerous roses. Since his name was Dale and the roses were so lovely, the townspeople settled on the name of Rosedale.