I have quite a few Rollers, and have shot them for many years. But I think you need to look at a Rolling Block's function again Don. What you described bout a Rolling Block dropping the hammer when the breech block is closed (if you've pulled the trigger first) is true. But the second part about the block being pushed closed on a case and the gun's ignition of the primer causing the breech to strike back and break the shooter's thumb is just plain impossible!
As soon as the breech block closes enough to allow the hammer to drop, the design of the Rolling Block allows the hammer to be dropped. As soon as the hammer drops it falls behind the breech block and prevents the breech block from moving. If the breech block could move as you described, it would open up upon firing and you'd have a face full of cartridge and hot flames! What you described is impossible in a working Rolling Block.
Furthermore, a Rolling Block does not have a sear! The Rolling Block design uses direct contact between the trigger and hammer. No sear used in between, nor is one needed. Here's a good diagram that shows how the Rolling Block design safely blocks the breech block when the hammer drops. Might want to study it, and before telling that tale.
And here's what DeHaas had to say about the Rolling Block design:
"In all Remington Rolling Block actions the breech block closes the rear of the chamber, but it is the hammer which holds and locks the breech block closed when the rifle fires. Thus the hammer has to functions, to lock the breech block closed, and to fire the rifle."