Kudos to them they took some initial to work on their mobility.
Thoracic spine extension foam roller.
Thoracic spine foam rolling exercising with a foam roller can help relax tight muscles and improve flexibility and symmetry.
These mobilizations will improve the ability for you to extend and rotate through your thoracic spine taking load off of the lower back muscles and spine.
About 18 in length.
Rolling back and forth horizontally relaxing with it lengthwise along their spine to open the chest or even some typical extensions mid thoracic.
Thankfully thoracic mobility can be easily maintained and improved using a foam roller and the thoracic spine extension exercise as described below.
Lie on your back.
How to do it.
I personally would have no problem with a patient telling me that they use a foam roller on their thoracic spine.