Use this link, or search for triggercmd on your Roku.

Unlike most Roku channels, the TRIGGERcmd channel does not play videos on your TV. It let's you run your TRIGGERcmd commands on your computers. It will list all of your commands by default, or you can check the "Have Roku channel display panels instead of computers" checkbox in your profile and it will list the buttons on your panels instead.

For example, I use it to turn on lights in my TV room using the TRIGGERcmd Smart Home Alexa skill's ability to trigger Alexa routines when your commands run.

You could also use your Roku to run this command on your computer that plays a Youtube video on your Roku like this:

curl -v -XPOST "http://(roku IP address):8060/launch/837?contentId=A7vYpIjfyYE"

That plays this Youtube video on a Roku:
https://www.youtube.com/watch?v=A7vYpIjfyYE