Kudos to them they took some initial to work on their mobility.
Thoracic spine extension foam roller.
How to do the thoracic spine extension this exercise will help stretch out the chest and back muscles relieve muscular tension and maintain thoracic mobility.
Bend your knees and place your feet on the floor.
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.
Lie on your back.
I personally would have no problem with a patient telling me that they use a foam roller on their thoracic spine.
About 18 in length.
How to do it.
Rolling back and forth horizontally relaxing with it lengthwise along their spine to open the chest or even some typical extensions mid thoracic.