Have you sent in a system diagnostic , and call Sonos Support to discuss it?

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution. Unfortunately, other than suggest that for some reason, it’s not getting fully charged, there jus isn’t much this community can do. 

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.

In the phone/pad controllers, look at the ROAM charge level. On occasion I notice the chargers, SONOS or 3rd party will get into a state where they are not effectively charging the ROAM. In this case the assumption that, as you remove the ROAM from the charger it is fully charged, is not correct. A simple reboot of the charger has fixed this. Unfortunately, you’ll still need to wait a while for the ROAM to fully charge.

What do you mean by reboot of the charger?

Briefly remove it from power. I suppose in some cases you may need to completely isolate the charger by also removing the connection to ROAM.

Talked to the support and they replaced it 

Did they replace the Roam itself or the charger? My Roam also drains in under 15 minutes. 

If you are out of the warranty period Sonos probably wont help.  Looks like your battery is toast!

I had the same problem here on my 2+ year old Roam (bought July 2021), the fix was to replace the dead battery, it was a fairly simple fix and it now works OK. I followed a youtube video showing the steps to take it apart. Bought a replacement battery off Amazon for about £25 so thats the cost of my fix. Apart from the new battery all you need are 2 torx drivers T6 and T10 sizes and a couple of bodgers to prize the bits apart. Just be careful undoing the cable clips (one for the speakers and one for the battery), there is a tag to depress to remove the plug from the board.

This was the tube video I watched -
 

Before trying some diy stuff I recommend contacting Sonos support. I can confirm for myself and many other users I talked to that Sonos is very accommodating in case of Roam battery issues even out of guarantee. Just my personal experience…

Fair comment if you get lucky with Sonos. Mine was over 2.5 years old. Additionally, the DIY repair whilst inexpensive, does make its waterproof feature questionable, I won’t be letting mine get wet!

@captainhaddock 

Just to clarify… I definitely would try what you did instead of buying a new roam, but as the easy way I just would ask Sonos for help before a diy battery replacement. 
I had some really good support experience with Sonos.