Solved! Roku Miracast Projection from Windows 10 had no audio

  1. Go into the device manager
  2. Find Miracast Display Drivers
  3. Uninstall the offending device  
  4. Right-clicked Miracast Display Devices
  5. Select "Scan for hardware changes".  This reinstalled my Roku Miracast device.  
  6. The next time I did a "Connect" to the device it worked!!!