Spectrum conked out for a few hours this afternoon, so I sat down with a book and went to turn on Roon, to access all my local music files - but nope!
It might have to do with the idiosyncrasies of my own network, but - do the Roon designers expect it to work in an environment without Internet access?
Yes, it should work without internet access. Roon will need access to your local library, of course. What is in your database won’t be updated, but it should still be functional. Roon will need to call home to validate your license at some point (within a month).
What are you seeing?
Signal was back within an hour, so I was almost just curious. Roon couldn’t see my core, which surprised me. I hear you saying that’s not expected, so it’s probably an unrelated oddity on my LAN.
Yeah, I suppose the outage may have messed up the router. Glad you’ve got music again.
I would like a definitive answer , all previous comments were it just needs to check back for license “occasionally “
The other day I restarted my router , then the core before the router had completed its “warm up” ie no internet connection, Roon meanwhile started but failed.
5 minutes later Roon started normally once the Internet was up.
This is not as I would expect from previous comments
Is this definitive enough for you? 
My Roon core doesn’t load without internet. Just assumed it was required. I only use local files. Is this a settings issue in Roon or more likely something else?
Tbh my internet is rarely out so not important for me personally.
I suppose it is possible that some versions of Roon require internet access during the startup phase. Once Roon has started and is running, then it should not be necessary.
I 've just removed the ethernet cable between my router and the fibre-optic modem connected to my internet, and Roon is happily playing and displaying all my local content. It is also displaying all the Qobuz content I have added to my library, but naturally it complains that it can’t play any of it because there’s no internet to stream it over.
This is with my Roon Core being on a ROCK/NUC setup, and the NUC is on 24/7.
I think what happens sometimes is when your internet goes down its still has a connection upstream but for instance the DNS server might be down. This half way house confuses my network as well.
Roon continues to work when I have ISP issues, but its uber slow, presumably trying to get info and get to tidal.
We had rolling blackouts a few weeks back that also took out the cable/internet provider for hours at a time. UPS systems kept the electronics going until the generator came online.
The Nuc/Rock continued to function with local files, probably because it was already up when the power went out. That was the only entertainment we had for 4 hours at a time. Don’t know what would happen if it was started up without the internet connection.
Android and PC remotes would start up and try to open the sections requiring the internet, New releases, etc. There was a pause with the pulsing roon icon then the app would continue startup and function with local files.
The IOS app startup would work similarly up to the pulsing icon but it would lock up instead of continuing. The IOS app was non-responsive and had to be terminated on the IPAD. If the IOS app was already up when the connection was lost it would continue for a while until it needed a refresh from the core then it would lock up solid and require termination.
I encountered the same problem yesterday. The internet was down at night because of a problem on the providers side. ROON running on a dedicated server working properly (started after internet was down), the music files on my Synology NAS also accessible without problem on my home network. Auralic Aries as an endpoint also working fine.
The ROON app on my iOS tablet for ROON control freezing constantly (kill, reboot… without effect). Not usable.
Control via server possible but very slow and of course far away in my office.
I would very much appreciate a comment on that. For me this is a question of continuing working with ROON or changing my music server. There is from my point of view virtually no sense of maintaining a personal music collection that can’t be accessed like normal when the internet connection is down.
I ran into the same issue here with my Roon Core (up to date and running on Windows). Our ISP had issues that lasted over 24 hours and interrupted our connectivity. I leave my Roon Core up all the time because it’s used throughout the house daily. I surfed my local library (HDDs mounted in Roon Core) and it worked for an hour or less and then would not play anything. The UX worked, it found the music files, showed the length of the tune that is supposed to be playing (even the Play button turned to a Pause button, indicating it was actively playing) but it wouldn’t progress the song. Time counter stayed at 0:00 and never moved.
Once the Internet service was restored, Roon came back on its own.
This clearly demonstrates (at least in my case) that Roon will not play local files unless it has an Internet connection. That is a show stopper and potentially game ender for me. One of the reasons I bought into the Roon eco-system was to take advantage of centralizing my relatively large library and being able to use it separately from any outside connectivity. If that doesn’t work, Roon is NOT for me.
I’d love to see a response here from someone who’s actually with Roon to clear this up.
Your not alone, quite a few of us have issues with it when there is no internet. Mines the remotes dont connect and just lock up as the Valence side can’t cope with it being down. So I can’t play a thing. Have to revert back to UPnP that works with no problems.
Has this been definitively answered by Roonlabs??
Why need a definite answer by Roon? 
It is a simple test, just unplug your core from the internet and see what Roon ist doing. 
Last time we had an internet outage the IPAD remote would not function. My W10 laptop and Android phone remotes did continue to function with local files after recognizing streaming options were not available.
I put a support ticket in at the time but as far as I know there hasn’t been any response from Roon on the issue.
and did you quitt Roon?
For me personally it is not a biggy.
So much rely on a working Internet connection.
If the internet is gone I will pick up a book and start reading. 
Simply disconnecting the serve from the net is not going to replicate the issue and I bet it would continue to function. It’s when Roon think it should have internet but does not. It just goes belly up.
I have worked out to sign out of tidal this can sometimes get it working to an extent but it’s not a good time.
In short, no. Roon does not work if the internet is down.
Roon did work for us during a severe freeze with rolling outages, 4 hours off then 4 hours on, that lasted for several days. We have a whole house backup generator that kept us going and Roon with local files was all we had during those 4 hour periods. The internet provider apparently did not have backup power so it always went off shortly after the power did. Always the same, IPAD remote did not work but the laptop remote continued to function.
I know Roon would have quit working if during those periods it needed to use the internet to validate my subscription. That in itself is disappointing with the Lifetime subscription.
It’s dependent on your home network set up and so there is no easy answer.