I am streaming , how can I play music when provider goes down.

@zappas  8-track had to sound better than cassettes because they were BIGGER, right?  So said meeself at age 17.

I copied 250GB (800 CD rips ALAC) from my computer to my phone. I can send music from it to my network player via AirPlay (Bluetooth) if there’s WiFi issues. Plus, my files are backed up on another device (phone) and they are portable.

Turntable and streamer with hard drive. I have an Innuos streamer that holds 2500 albums. You can rip (copy) from a cd or from the the streamer. 

I just have a fanless computer  running Roon,qobuz and separate dac 

The Qobuz app (Mac, PC, or mobile) has a built-in facility to download music that be played offline.

https://help.qobuz.com/en/articles/10133-is-it-possible-to-listen-to-music-without-internet-connection

To use it, you need to run the Qobuz app as your music player instead of Roon. Music files that you download (Qobuz uses the term "import") are encrypted and can only be played by the Qobuz app.

If you prefer the Roon user interface, perhaps you could switch over to the Qobuz app only while your internet connection is down. You can pre-download (import) enough music on Qobuz to get you through periods when you have no internet.

Get an Eversolo DMP-A6 and install a 2TB m.2 drive internally, then copy your music onto that. No network required. Someone else mentioned Blusound, get a Node, and an M.2 drive in an external USB enclosure, ditto.