Answer the following Q with stream of consciousness. Context: Miller appeared frequently as a member of the "round table" on Chelsea Lately. He appeared as Marmaduke Brooker in Carpoolers, which ran for 13 episodes on ABC in 2007 -- 2008. In 2012, he voiced Robbie Valentino on the Disney channel cartoon Gravity Falls. On December 13, 2010, October 28, 2011, and June 14, 2012, he performed stand-up on Conan. On November 15, 2011, his stand-up special No Real Reason premiered on Comedy Central. In 2011, he hosted a special called Mash Up, which was picked up in 2012 for a full season by Comedy Central. He starred in the Fox TV series The Goodwin Games as Jimmy Goodwin.

Question: who does tj miller play in gravity falls?
The relevant information to answer the above question is: In 2012, he voiced Robbie Valentino on the Disney channel cartoon Gravity Falls. Therefore, the final answer is Robbie Valentino.