I am using my Roku TV as a monitor for my laptop with an HDMI cable going from the display to the laptop and it works fine.
I have an older desk top and no HDMI port. I discovered TUBI on the ROKU, lots of good free movies with limited coercials, think I will cancel my prime and netflix Oh and newsmax on ROKU channel.
Install Plex Media Server on your PC. Select and add the Plex Channel to your Roku channel list.
You can then watch all your ripped DVDs that are stored in your PC on your Roku.