Downloaded Roon to my iMac, I get the download image, double click it opens to two images. The Roon logo and applications logo, click but no software opens. I am not a computer expert, so I am about to give up.
I found this information in another post
Are you opening the Roon application from within the dmg disk image?
This behavior sounds like it. If so, copy the Roon application to your Application folder and try to open it there.
If this happens when double clicking the Roon.dmg file: Check if really nothing has happened. .dmg files are very common to distribute software applications. They are disk images and when you open a dmg file a new volume should appear that contains the actual app.
So, check if there is an additional volume by clicking in the Finder on “Go to” (in the top menu bar) and select “Computer”.