After endless purple screens on a Roku premier and Youtube I started looking for anything that would make life easier.
Here is one short cut that works every time that will get you back to the YouTube menu system without starting over again after the purple lock screen, after purple lock screen press * <- <-
Asterisk, back arrow, back arrow will exit the purple screen and put you back into the YouTube selection menu.
Now for the unbelievable, unreproduceable (after reboot) , I was able to turn off the purple HDCP screens for all 4K content using the navigation keys and the OK button.
Don't know if it was 5 or 6 keystrokes but it ended with OK and the up arrow, may have included a back arrow ( top left ).Did this twice by accident / chance. It was wonderful watched 4K content for over a half hour.
ROKU Premiere Plus ROKU 4 ROKU 3 Tablo OTA DVR Samsung 4K UHD TV Hisense 4K TV