I don't think that is the issue. Sure, over-revving causes valves to float and hit the pistons... that is not the same as valves rolling. I was told the the exhaust valves show the slow progression of the deformation when they are all out and you can compare to the valves from other cylinders. Over-revving causes an immediate valve failure that bends the valve or the edge of the valve towards the valve seat. These valves are failing by bending the opposite way - away from the seat. This means the valves are failing by hitting the valve seat, not the piston.
I haven't seen the valves in person yet so I am going off what the tech said. They are saving the valves and have taken pics of the cylinder walls, pistons and other items of interest since i cant be there to see it myself. Once I see the valves and pics for myself I will let you know if the damage is consistent with floated valves.