I m having the same issue as the OP. The Roku channel on my Roku TV will not load. Other channels load fine.
I tried removing the channel and reinstalling it according to directions posted in this thread and the issue remains. It is only the Roku channel--all other channels are fine and launch/play with no problems and I am able to view content.
Restarting the channel sometimes helps launch it but often (mostly) does not help.
Occasionally, after much time I can get certain parts of the ROKU channel to load (only after getting a prompt to reload content by pressing OK) but the HOME screen of the ROKU channel, which contains the shows I am currently watching, will not load. Also, anything I can get to load will launch painfully slowly or not at all.
I can only get it to play after much fiddling--many times trying to launch the app, many times waiting to see if content will load, then when it finally does I hope the Home screen loads. Then I need to watch what I want to quickly in case the issue begins again.
I have nothing to add here, so this is my report.
ROKU channel version 8.0 build 72
Software version 11..5.0, Build 4312
65" Hisense Roku TV (Costco model #65R7G5)
OTA TV antenna (indoor $20 RCA rabbit ears)