I have a TCL55P605 TV with Roku built-in. I have an input named "Computer" (on HDMI 1) that I set up on the initial config wizard thingy. The TV is linked the normal way through my.roku.com and then through the Home Android app.
When I say "Hey Google, switch to Computer on Roku" it it switches to the Computer input but then blocks off the upper right part of the screen with the notification "Use the Roku remote to get a full list of results" for 10 or so seconds. Pretty annoying! lol
When I say "Hey Google, switch to HDMI 1 on Roku" it works fine with no annoying notification.
Please fix! 
PS: Really wish the Google Assistant responses to commands had an option to be more basic like a simple beep or "OK".