Did your Roku TV decide to strong arm you into giving up your rights or lose your FULLY FUNCTIONING WORKING TV? Because mine did.
It doesn't matter if you only use it as a dumb panel for an Apple TV, Fire stick, or just to play your gaming console. You either agree or get bent.
Ah yes, airgap the streaming device.
I believe it is possible by simply attach a rooted device to the TV with streaming capability, like a computer, or a rooted nvidia shield.
Although I don't agree with OP that everything needs to be rooted, for example, my phone runs grapheneos without root, I do believe most rooted OS are more usable than proprietary OS like Roku.
It can still stream video over the hdmi port just fine. This is about containing the rooted malware inside the tv's firmware from exfiltrating and then self destructing.
My TV streams my shows just fine via my xbox