Roiland became heavily involved with Dan Harmon's Channel 101, a short film festival where creators compete for a monthly time slot. He created and starred in various shorts, refining his improvisational and comedic skills.

Roiland worked as a writer, storyboard artist, and voice actor on various animation projects. Specific details of these projects are sometimes unclear, but this period marked his early professional development.

Roiland created 'House of Cosbys,' a pilot for Adult Swim that garnered attention. Although not picked up for a full series, it showcased his unique comedic sensibilities and animation style.

Justin Roiland was accepted into an animation apprenticeship programme at Cartoon Network Studios.