New Smart Monitor being controlled by Roku

I recently purchased a Samsung  27" M50B FHD Smart Monitor with Streaming TV . I have a Roku connected to my TV, and don't plan to use it to watch things on my PC smart monitor.  The problem is, when I have the TV on and turn it off, my PC goes off. When I change the volume up or down on the Roku/tv, it changes on my PC. How do I stop this? Thanks in advance for any help.