@KPyall
The USB cable on the Roku 3600 is simply for providing power to the Roku device.
It really can't assume anything (it doesn't know where it is drawing power).
You can try using a longer micro-usb to USB-A cable and then a 5volt, 1amp USB charging adapter (like a cell phone charging adapter) and plug it directly into the wall outlet and see if that resolves your issue.
Roku sells a 5ft cable, but you can find them in just about any electronics dept in a store. https://www.roku.com/products/accessories/roku-micro-usb-power-adaptor
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Your Pi may be either entering into a sleep mode/suspend mode that is cutting power to the Roku device. Depending on the build and model, you may need to look at the Sleep, Idle, or Halt settings. You can try adjusting the Pi's power settings if you wish, or just use an alternative power source to provide continuous power to the Roku device.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
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