Miracast is a wireless standard, allowing you to mirror your screen to another display using Wi-Fi. A simple way to think of this is "HDMI without the cable"; your computer connects wirelessly to your Roku to send the picture and sound to display on your television.
2. Screen Mirror from Windows to Roku (Miracast)
Open the Action Center.
Click on Project.
Next, Select Connect to a wireless display.
If the Connect to a wireless display option is not listed, this means your device or video card does not support Miracast. If Miracast isn't supported, we recommend connecting directly with an HDMI cable or other methods.
A scan for wireless display devices will start. Select your Roku.
Once connected, your Windows 10 device should now be mirrored by the wireless display.