Are you certain you are fully powering off the Roam device with a 5+ second power-button press until you hear the 4-tone descending jingle as shown in this YT video below, rather than placing the device into standby mode?:

@Ken_Griffiths 

Even if you switch it off completely a simple press of the on/off button boots the speaker on again and then it's empty a few days later, right?

It’s also perhaps notable, that there are a variety of carry cases for the Roam aswell, which perhaps make it far less-likely that it will be powered on whilst being transported in a bag. See this one (of many) such examples:

 https://www.amazon.co.uk/Khanka-Travel-Replacement-Bluetooth-Speaker/dp/B08ZKG3K9H

No, the Roam’s power button requires a much longer-press to power it on from its powered off state, whereas it only needs a quick-press to resume from standby.

@Ken_Griffiths 

Thank you Ken. Much appreciated.

I'll keep playing around with it and see how it behaves.

Also, just to perhaps assist further… In its fully powered off state the Roam’s li-ion battery-drain should be around 3% per day (depending on environment temperature) and so should remain charged/ready for use for weeks whilst in that mode during its transportation.

It takes a good 7 seconds to power the Roam completely. After 2 weeks in this state my Roam is at 87%. 
 

However it only takes the slightest of touches to the power button to turn it fully on. Any carry case needs a solution to protect the button. 
IMHO the best solution for me is to buy the Roam wireless charging bases and leave them on that till I want to use them, much the same as how I use the Move. 

Thank you @bockersjv.

As stated I believe the power button should be some kind of recessed or protected from accidentally pressing.