@Marksw-
The screen you are describing with buildings sounds like a screen saver.
Rokus plugged into constant power supplies don't turn off when you turn off your tv. If the Roku went to the screen saver due to inactivity after you turned the TV off, or moved to a different TV input, that could be where it is when you turn your tv back on.
You can prevent your Roku from going to the screen saver in the first place by going to Roku menu path Settings > Theme (may take a few seconds to load) > Screensaver start time > Disable screensaver.
Note that this could leave your Roku streaming unwatched stuff and using a lot of unnecessary bsndwidth. To limit this to no more than four hours you can enable 'Bandwidth saver' under Settings > Network.
Further, you can eliminate unwatched downloads altogether by getting in the habit of pressing the Roku Home key to return to the Roku home page before changing to a different input on your TV or turning your tv off.
Roku Community Streaming Expert
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Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X