If you can successfully follow the steps below, you will not have to factory reset your Roku device. If your Roku device doesn't show the intrusive update screen, and you don't know how to manually update your Roku device, you'll find that information at the bottom of this post.
Intro:
This is an updated post after having visited with my parents who had different Roku devices than me. I decided to delete everything in this post that no longer applied to my prior situation as I had solved this issue on my device (Roku Express Plus 3910RW) and two of my parents' devices (Roku Express 3900) that were affected by this. The two that were of the same model (Roku Express 3900) weren't affected since they had auto-updated and restarted themselves a week prior after having been left on for months. So it's possible that if you leave your Roku alone when you see that update screen and just let it then automatically update, your Roku device may update the OS without any issues.
I don't know if the solution below works for all Roku device models, but this is how I solved this issue on the devices listed above.
The issue:
When I turned my Roku Express Plus on today, the Roku told me I had to update. After tapping the remote to allow it to update, the device then errored out and showed that blank wallpaper screen. When I turned on my parents' Roku Express devices and went to manually update them, the Roku OS update errored out and showed the same blank wallpaper screen.
