They might need an online copy for Roon mobile, if it comes, but certainly my Roon works normally without internet and I am sure this remains a user expectation, so I don’t see how the metadata and art can be just online. In any case, if the database is fast enough when only online, the whole concept of a local Roon Core would not be be necessary in the first place
Don’t think so. Anyway, my fanless NUC is always on and my carbon footprint is minimal elsewhere, but if someone wants to save some CO2 or money, I do understand the wish. It’s just very little
turing off my nuc/rock at a scheduled time does not sound appealing to me. imagine a longer listening seesion than usual and suddenly it gets all quiet…
I simply press the powerbutton and be good. Dont have a bad feeling when i forgot it once in a while, but usually rock is sleeping when I do 
Being able to switch rock Off and ON from whithin the Roon app would be cool though!
Cached. As now with albums art.
Exactly. A “local Roon Core” seems to be where most of the end user problems are anyway, move it to “the cloud”, and you’ve fixed that - plus, you’ve conveniently enabled “Roon mobile” in the process.
Yeah, but I’m not seeing it any time soon