I didn't realize it was a Roku-TV. If it's completely standalone, then it's something between the service company (not likely), the router, and the Roku-TV. The fact that it can work for days makes me wonder if your router and TV are communicating poorly. If a TV is in another room from the router, the 5GHz can have a hard time getting through some walls. That's the reason you would use the 2.4GHz. Us the 5GHz if it's in the same room because it's astounding how much more information you can receive over a 5 vs 2.4. Also, if it's on a 2.4GHz, then so is the microwave and most old telephone sets. I've gone through this personally where you have too many devices on these bands and then you start working with Channel settings inside the Band. You feel like a communications specialist after a few days of studying all this stuff. Everything from how many wireless computers, printers, smartphones, etc... My Smartphone and television did not like each other. Set all the Smartphones to different channels inside the 2.4GHz and all the computers and printers onto the 5GhZ. Then the Roku in the same room with the router to 5GHz and the other television in the living room on the 2.4GHz. As I said, it took several weeks of reading all this technical stuff before everything worked like a charm.
This is one of the reasons customer support just won't answer the phone anymore. Just who's problem is it . . . everybody and nobodies.