Not going to happen. Comedy Central just pulled the Daily Show off of Hulu. I guess they felt their own site was losing too much traffic. They are not about to let the Daily Show play on the Roku. The quality of the encode for the Daily Show is terrible. I wish they would fix that (and make it 16:9).
Not going to happen for free
. Comedy Central currently has the Daily Show and Colbert on itunes for $2/episode or $10/15 episodes. In theory something similar could be done for the Roku. Not saying it will happen, but it's not out the of realm of possibility.