Killing microbes or fungus, or curing glue, or whatever in a microwave
oven can be a tricky proposition. Heat is induced in a microwave field
by the translation of absorbed energy to the rotation rate of dipole
moments. What this means in simple terms is that heating is directly
proportional to the dielectric constant and indirectly proportional to
the thermal mass of the molecules being heated. Additionally,
electrically conductive objects reflect microwave energy and will not be
heated because no energy is absorbed. The problem is further complicated
by spatial variations in microwave field density caused by beam design
and reflection artifacts.

Sticking a piano roll in a microwave oven and hoping that it would heat
evenly to a temperature sufficient to kill bacteria or eliminate odor
causing fungus is an unlikely proposition. Paper has a fairly low
dielectric constant. Heating of the paper by microwave energy would be
almost nil. The spool may or may not heat depending on it's composition.
Some plastics would melt but cardboard would heat very little.

The reason most foods cook in a microwave oven is that water readily
absorbs microwave energy. Foods having a water content will heat. Dry
foods will not.

If one were really determined to heat piano rolls in a microwave oven,
perhaps they should be soaked in water overnight. Of course this would
disrupt the paper ligature and the piano roll would probably be
converted to a cylindrically shaped blotter, after drying with the
microwave.

I suspect that there are better ways to treat a piano roll.

Bill Finch