Funny you mention that. The roller and pin that goes into the side of the shuttle "disappeared" (my bench is the black hole...) during another change-out. Just fell out of the side of the shuttle.
Fortunately, the roller/pins are intechangeable between the small and large primer shuttles, so I was able to do a quick change-out when I needed to change primer sizes. It turned up a few weeks later...but I agree, they'd be a good thing to have.