Like others, I have seen my rokus give me a message that they do not have an internet connection. While other apps on my Rokus stream with no issues, the Spectrum TV app would play for about an hour then disconnect. I did two things. First I installed a wireless internet extender so I get 5G signal on the second floor of my house and second, I disabled QOS completely on my router (I have a combined modem/router box from Spectrum). I rebooted the modem/router, and the Rokus. So far so good. Three days of solid connection and the Spectrum TV app has been playing today, for example, all day on four TVs without disconnecting. What a blessing. I wanted to share these two things with everyone in case someone has had the "no internet connection" error message and wants to try what I did. I was ready for Sling or some other alternative but so far now, so good.
This is why wireless is useless for permanent devices and ethernet needs to be used.
The all in ones are horrible with internal antennas
It's possible the dhcp lease was set for an hour not a day, or you have Wireless congestion/ interference from cordless phone, baby monitor, microwave oven, etc.
I would set QOS at 50% so that no device can hoard all the bandwidth