Shouldn’t be hard to do, but both turntables will need a pre-amp before their signals can be fed to the line in on a Sonos device.
 

Current devices with line-ins, in no particular order: Era 100, Era 300, Sonos Port, Five, and Amp (I think that’s all right now).

You could conceivably go even odder, and convert the music to Bluetooth, and then feed a Roam that signal to be shared with all other Sonos devices on the network. If you believe in rumors, The Verge says the next version of the Move will be able to do that as well. 

Several Sonos devices have a single RCA input, non of them have phono (no preamp required) inputs.  Those are  Port, Amp, Era 100, Era 300, and Five.  So if you get 2 preamps, and 2 of the devices I just listed in any combination, you can connect both turntables.

There are lots of other possibilities if you want to use some sort of RCA switch, preamp switch (if that exists) or bluetooth that might make more sense for you.  Can’t really say what the best solutiion is for you without knowing more about where you want to locate the turntables, what Sonos you have or want to get, and any other requirements for your specific setup.

Just wanted to add that Era 100 and 300 can also share bluetooth audio.

Two turntables suggest you may be attempting to DJ.  If so, Sonos is not a great platform for DJ’ing, or any other live performances.  The analog Line-In is going to add at least 75ms in order to buffer the input for streaming to multiple rooms, and that delay makes it almost impossible to synchronize your DJ moves with the sound being heard.

It’s difficult to think of a speaker system less suited for DJ work than Sonos. 

I was focused on the connection, not the use case. 

I don’t recommend attempting to use SONOS for DJ applications, but if you want to continue along this path, add a preamp for each turntable and connect them to a mixer. The mixer output can be connected to a SONOS Line-In.

I appreciate the insight into the Sonos/ DJ application experience.  I have been hesitant to attempt an integration of my turntables from my previous wired monitors located in my in-house music room set-up into the rest of my whole-home Sonos system. 

I recognize the buffer delay throughout the wireless home system could kill the experience.  While I really don’t utilize my decks for DJ-ing anymore, and only have one currently set up in my music room right now, I have been watching the Sonos line evolution and have been curious if anyone did specifically have experience with pre-amping in 2 turntable decks into a Port, Five, Amp or Era 100/ 300.  My curiosity piqued recently with the release of the Eras as I am considering adding a couple 300s into my Sonos home system which already exists of Ones, Moves, Arcs, Subs & Moves. 

Thanks so much for the recommendations on the pre-amp accommodation for the multiple line-in requirements of 2 two turntables.

Not your gear, but long ago I used a mixer to allow me to feed several audio sources into my ZonePlayer. The powered one I used had no issues, the passive one was a bit weak on volume passed to the Sonos.