Yes it’s fine to leave the Roam on its charger according to this post here from Staff:

Hey thanks @Ken_Griffiths , but what if its plugged in via the USB-C charging, not the wireless charger. 

That is also fine 

Alright thanks @James L. ! :)

I'm unsure if it's wise to leave any charger constantly connected as I thought it was a fire hazard? I'm open to being convinced otherwise. 

Unless it’s a poorly built charger (not sure if you’re talking about a Sonos device, or something else), and it’s plugged in to an appropriate wall plug or U/L listed extension cord, there should be no additional hazard. 

However, there are certainly poorly made chargers that can be purchased on the cheap that are not U/L listed that I’d be concerned about. At the end of the day, you get what you pay for.