Sonia Bravia - Roku Streaming Stick 4K - USB Power
If the USB port on the TV supplies at least 1 amp (1000 milliamps) it should power a Streaming Stick reliably. I can't find anything online about the USB power level on a Sony Bravia 55X90K, but it might be labeled right on or beside the port itself.
Besides the power level there is another consideration. If the port shuts down when the TV is off, as many do, your Roku will have to start up from a full powered down condition each time you start the TV. When the TV first starts up it will check its HDMI ports to see what is attached. On TVs that start up quickly from a low power standby state the HDMI port may be checked before the Roku has started up far enough to connect to the HDMI port. This can cause some TVs to post a "No Signal" or similar warning on the screen. Changing the TV to a different port and back will often cause the TV to check the port again and find the Roku. The way around this is to power the Roku from house power so that it stays on all the time and is ready to go when the TV starts up. It also permits the Roku to check for and receive regular updates during normal down times.
