Just get a programmable outlet or outlets for the Roku & router. Program the outlet to turn off & back on every day. Some routers have a auto reboot feature built in.
Something like this. https://www.amazon.com/Techbee-Countdown-Programmalbe-Electrical-Appliances/dp/B086DN9QT3/ref=sr_1_5?keywords=programmable%2Boutlet&qid=1679925698&sr=8-5&th=1
Last week, my new Roku Ultra 4K started playing video in a one inch square screen in the upper left corner of the screen. The app screens were full screen. Turning off the power saver mode solved the problem. I started using the Ultra in November of last year. It worked fine until last week.