You used to be able to do so on the home screen by pressing the * button to open the menu, but I just checked and that's no longer there. I then tried the channel store, both the web page and within the device. I couldn't find any way to make a rating. I'm not certain that ability still exists. And to the best of my knowledge, a user could only leave a rating, I don't think there was ever a way to leave a text review of a channel.
Dan
Roku Community Streaming Expert
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