Roku remotes are sophisticated devices. There are many models, so features vary, but among the possible features are 3.5mm audio output, Bluetooth audio, voice command input, Wi-Fi, infrared, battery charger and other things. Clearly a substantial MCU is present and thus, an RTOS.
Pretty sure they don't have gyroscopes and accelerometers anymore, but they did early on. It was basically a Wii Mote and I played a ton of Angry Birds on my TV.
On my rokus, I am able to use my phone as a remote via the roku app. This includes typing on mobile via my phone's keyboard. Makes logging into things much easier.
And much, much better, as well
Why does a remote control require a RTOS?