Rolling Locomotives

Probably a dumb question, but here goes:
Take C&S No.9 as an example. Ancient rust bucket, been sitting dead for MANY years. Someone decides it needs to be moved. Do steam locomotives lock up from corrosion?
Same concept applies to deadheading, ... with all that valve gear and the pistons / cylinders themselves, one can't disengage all that like one might put an automobile into Neutral. The point of disengagement is between the boiler and the cylinders, leaving all that gear engaged and in need of lubrication when in movement.
So how does one go about properly moving a dead locomotive? Do they roll freely ? I guess what got me thinking about this was getting No.9 onto a truck and hauling it around. Wasn't it half past crusty ? I pull cars out of fields (and garages) that are locked up like a brick and have to be dragged onto a trailer. But cars have rubber tires you will replace anyway. Dragging a locomotive seems like a real bad idea!
Help this confused old dude!