Rock and Rollers. And Oil.
Fox Bassoon thumb keys
I cannot tell you how many times I have struggled to remove a key roller. Every other mechanism on the instrument may be well oiled, but somehow the poor rollers are so very often neglected. Like any other steel that is exposed to oxygen, the rod that secures the roller rusts, sometimes so badly that the plastic roller seizes up. So next time you send you instrument in to your friendly neighborhood repair center for a PC job, ask them if they can spare a drop or two of oil for the roller.
Shown above is the right hand key set on a Fox bassoon. Note the two black pieces on the keys, those are rollers. They are utilized to eaze sliding your thumb on and off the mechanisms. Flutes, saxophones, and harmony clarinets use them.
Disassembled (and not lubricated) roller
Inhorn Band Instrument Repair 