I've never seen anything that indicates the Roku is using profile-based color management. I know if I want to match a graphic to a spec'ed color in the UI, I profile it with NTSC(1953). The screen shots I've gotten are not accurate either, but I don't see how they would be. They should however, be consistent so you can set up photoshop actions to fix them.
I've seen the discoloration too, and it looks like some sort of anti-alising issue to me. I doubt Roku put a lot of effort into this feature, I wouldn't expect it to spit out perfectly rendered, properly profiled images.
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