Yesterday at customer's home I noticed a power button on the mobile app for the Roku 4. So i loaded up a tablet emulater on my pc and ran wireshark and I was happy to see that the power button was on the app. I pressed it and found the power code.

This is a power toggle
$ curl -d '' ht tp://192.168.1.134:8060/keypress/power
Still power toggle
$ curl -d '' ht tp://192.168.1.134:8060/keypress/poweroff
Descrete Power On
$ curl -d '' ht tp://192.168.1.134:8060/keypress/poweron

I pulled up the device info by typing the following in my browser and got these two power indicators while the Roku 4 was in different power states.

ht tp://192.168.1.11:8060/query/device-info

DisplayOff

PowerOn

I now just tested it on remoku.tv with the following in the goodies section.
{"keypress":"power"}
{"keypress":"poweroff"}
{"keypress":"poweron"}

They worked. I tried a few other terms like standby and sleep, but they didn't work.

This came in handy with an install that had a Roku 4 to the theater room but he also wanted to share the Directv and Blu-Ray in the game room TVs. The Theater has a 4K projector so I set the Roku4 to 4K but the 22" TVs in the game room are 1080p. Needless to say I had some serious EDID issues. Being able to turn off the display was just one piece of the puzzle.