Hi,
as ROCK can be shutdown via the URL http://rock.local/1/poweroff I wonder, if I can use some API stuff like play or skip via an URL. Is this possible?
No. I don’t need an interface, just URLs 
Also the ROCK seems not to support extensions, so it wouldn’t help me. 
Why do you think Rock doesn’t support extensions? I know for sure it does.
I don’t know what you mean by an interface V URL. What I linked to is a web based (access via URL) Roon controller.
Roon Server on ROCK supports extensions alright, but currently there’s no facility for running NodeJS/Roon Extensions on a ROCK machine directly – they’ll need to run elsewhere in your network.
Thanks, so it’s no option for me as I bought the NUC to replace my iMac for music listening.
You could always ditch Rock and install a linux distro of your choice. Something makes me think that the ability to run other stuff on Rock is in the works though.