A replacement is about $50.

You could attempt to rinse and agitate it in distilled water, then rinse in 90% rubbing alcohol. Allow to dry thoroughly.

The pushbuttons are usually a conductive foam pad that presses on traces on the circuit board. If it's full of roach droppings, those could be partially shorting out the keys.

But it's likely it won't work correctly when you're done.

Highly recommend after wiring up the replacement, you squirt a glob of silicone to seal the hole.