Hi everybody,
First I like to thank Jan for your help in solving this. Because
I solved it. I’m not really sure what did solve it but now my Nas idles.
But I can describe what I did. I deleted an unused minimserver folder. Then I unclicked the WOL on Lan 1 box. After this I removed the watched folder in Roon. Restarted the laptop with Roon on it, added back my music folder that resides on My Synology 215j and waited 15 minutes without any music playing and lo and behold the Synology went to sleep.
Hope this can help anybody else who has this problem.