Loosen a stiff upper back before you ever touch a bar.
Keep your ribs down and roll the upper back only, never grind on your lower spine.
The roller sits across your mid and upper back, right where the thoracic spine tends to lock up from sitting, phones and heavy pressing. Rolling between the shoulder blades and letting your upper back extend gently over the roller restores the extension you need for a proud chest on squats, presses and rows. It is one of the highest-value two minutes you can spend before touching a bar, since a stiff upper back steals position from almost every big lift.
Small pops from the joints of your upper back are common and generally harmless, usually just gas releasing in the joint. It is not the goal though, the slow rolling and gentle extension do the real work.
Yes, it is a great pre-lift habit, especially before squats and overhead pressing where you need thoracic extension. A minute or two of slow rolling is enough.
Your upper back is built to extend and tolerates pressure well, so you can be more generous here. Keep the roller above the bottom of your ribcage and never let it grind down onto the lower spine.
