1. Ryan Adams - American singer-songwriter, musician, and producer
2. Ronnie James Dio - American rock singer, songwriter, and musician, best known as the lead vocalist of Rainbow, Black Sabbath, and Dio
3. Rob Halford - English singer, songwriter, and musician, best known as the lead vocalist of heavy metal band Judas Priest
4. Roger Daltrey - English singer, songwriter, and actor, best known as the lead vocalist of The Who
5. Rick Springfield - Australian rock singer, songwriter, musician, and actor
6. Robert Plant - English singer, songwriter, and musician, best known as the lead vocalist and lyricist of Led Zeppelin
7. Robert Smith - English singer, songwriter, musician, and record producer, best known as the lead vocalist of the rock band The Cure
8. Red Hot Chili Peppers - American rock band formed in Los Angeles in 1983