Go here: https://owner.roku.com/Add You probably have to log into your account first. Then in the box type in JUSTINTV, for justin.tv of course, and IN4DN for ustream. Then click add channel. After you've done that go to your tv and check your channels from the home page. They should be listed. It may take a few minutes or even a powercycle of the box for them to show up. Click on one of the channels find your players stream, if they are streaming of course, and BOOM SC2 ON YOUR BIGSCREEN!!
There is also one for blip.tv (so you can watch day[9] ) but it is on the add channel page of your actual Roku interface.
I'm watching the NASL finals on mine right now.
I'm sure there are other ways to watch without a Roku box, but my tv doesn't have the right connections to hook up to my computer.
Anyway just wanted to share with you guys in case you wanted to try it! I've been trying to find a way to watch streams on my tv for awhile now so glad I found this out.
Here is a link to a bunch of other channels for Roku box too. Most are free!
http://www.roku-channels.com/home