He played Jimmy James in NBC's NewsRadio & provides a voices of Bill Dauterive and Buck Strickland in King of the Hill. He has besides appeared around films including Office Space, Ice Age, Finding Nemo, The Ladykillers, Dodgeball: A True Underdog Story and O Brother, Where Art Thou?. Root too portrayed NASA chief flight controller Chris Kraft in the miniseries From the Earth to the Moon.

He is likewise a voice of Commander Chode on the Sci Fi Channel's Tripping the Rift.