William Roscoe Mercer (1927-2000), better known to millions of radio listeners simply as Rosko, was an American news announcer and disc jockey. He is best known for his stints on New York's WOR-FM and WNEW-FM in the 1960s. Rosko and other DJs of the time pioneered alternative-format FM radio, in response to the restrictive playlist programming of Top 40 AM stations.
Mercer died of cancer on August 1, 2000.