I just got a a new Ultra Roku. The picture quality seemed very distorted. I played around with adjusting settings people suggested here; though my old Roku still works ok and with a good picture. In hindsight, it was wasted time and did not provide a solution. I was on the verge of giving up; on assumptions of a bad unit or poor bandwidth. It didn't help that the remote on the new device is so sluggish by comparison to the old one.
Then...low and behold, I discovered that the NEW Roku automatically adjusted itself to a DIFFERENT PICTURE quality SETTING on the TV. That is.. it was set to the CUSTOM picture settings for my television. That was the problem. My TV custom settings had been set to extreme levels of bright, tint, background etc.. some time ago ( to see details on a very dark show). Since then, the custom setting was no longer used. By switching it to one of the standard picture settings (movie, standard, baseball etc.) it looks good now. Thought I would share as I can imagine others in my position.. bummed about whether to return their **bleep** picture ROKU and unaware its this.. hidden picture default link that could be the culprit.
Good info!