That’s obviously old, but why are you looking in Downloads. You’ll just find the (old) installer there, as you did. You should be looking wherever it is that Roon is installed after you installed it.
Yes, because there would be only the one Roon app installed even now, and the Control Panel shows installed apps. But the Roon app installs a Roon.exe and a RoonServer.exe program (and many other things it needs), and you should find them where Roon is installed, normally.
I don’t have Windows but probably similar to this (screenshot from the help)
The folder you have to go to is probably %localappdata%\Roon\Application or just %localappdata%\Roon
and it should look something like this, just that somewhere around there should also be a RoonServer.exe file in addition to Roon.exe. (The “.exe” is probably not going to be displayed on your computer)
(taken from this thread)