You need a Sonos device with Line-In like a Sonos Five, Sonos Port, or Sonos Amp. Your best option would be either the Five or Port. You also need a turntable with a built-in phono preamp.
Read more here:
https://support.sonos.com/s/article/3548?language=en_US
Since you already have a Roam, another option is to get a Bluetooth-compatible turntable (like this one) and connect it to your Roam over Bluetooth. Your Roam will act as a Bluetooth “gateway” and allow you to group your other Sonos speakers to the Roam and listen to the turntable audio through all of your speakers.
NOTE: You will experience better sound quality from the Line-In options above. You will hear a slight drop in audio quality with the Bluetooth option.
FYI… Sonos doesn’t make a turntable.