Many are reporting issues where their TV turns on to a black screen. If you mention a TV brand name, the Roku Web Bots will respond telling you it's not Roku's problem. It is happening across multiple brands so that points to a Roku Issue.
My mothers TV has the issue. Turning on the TV you will see the Brand logo then it goes to a black screen. No of my 3 Roku TV's have the issue, but the other day my wallpaper was black, but the Roku Menu was still showing. I went to the Theme/Wallpaper settings and saw they recently changed the entire interface for selecting wallpapers. I re-selected the Dynamic wallpaper that was black and that fixed it and now it shows. Now I'm noticing that portions of the Dynamic wallpaper will be black, but after moving around the menu the full wallpaper will come back.
I'm suspecting the changes to the Theme settings introduced a bug to certain model TVs causing the black screen.
UPDATE: All non-dynamic wallpapers are black after applied. It would be nice if Roku developers stopped pushing unwanted/unneeded features instead of fixing bugs. Every new feature they add causes more issues.