Help setting up Roku TV as 2nd monitor on desktop computer

I am attempting to set up a Roku TV as a second monitor on my desktop.  The settings show the monitor attached, and i have reduced the resolution and refresh as suggested on other sites.  However the monitor says no input detected "Is computer on?"

My desktop does not have an HDMI port.  I am using the same cord from before, which connected to the monitor with a 15 pin.  Then I have an adapter from 15 pin to HDMI, which is connected to the Roku.

I am wondering if the issue is the adapter?  Possibly I can't get video in to the TV from the computer due to lack of HDMI output?

I am not tech savvy, so please forgive any errors or ommisions!