Son of 3 times World Champion Kenny Roberts Sr. and younger brother of 2000 World Champion Kenny Jr., Roberts joined the 250cc World Championship in 1997 at age 17. He headed back to the US in 1998 and was crowned AMA Pro Honda Series Champion in 1999 and 2000, taking the Formula Xtreme title as well the final year. Roberts made his premier class debut in 2001 on his father's Proton 500cc bike as a wildcard at the Malaysian GP. 2004 saw Roberts compete in a full season in the MotoGP class – though his campaign was curtailed as he missed several races through injury. In 2005 he made a solitary appearance on his father's team, returning mid 2007 to help develop the 800cc KR212V, replacing his retiring older brother.