Plays electric and acoustic guitars for the Canadian band Barenaked Ladies (BNL), and more recently, performs as lead singer or co-lead, raps, and writes music and lyrics. Robertson is probably most easily recognizeable for his improv and rapping on BNLs single "One Week".

Some of Robertston's songs include:

"One Week" from 1998 album Stunt
"Am I the Only One" from Maybe You Should Drive

Robertson also co-wrote Barenaked Ladies' 2000 album, Maroon with fellow bandmember Steven Page.