You can use the same 3M insulation used by HVAC duct workers. It is fiberglass and foil faced. It comes in thin or thicker varieties. Here's the thing, however. You live in MO, so like Texas you get heat. Keep the foil side of that insulation at least 1 inch away from your roof and you benefit from the radiant barrier effect. If you need an example of this, take the lampshade off a lamp in your house which has a common incandescent bulb in it. Turn it on and stick your hand about 2 inches from the bulb. You won't want to keep it there long, because it will burn you. Now place a piece of common kitchen foil with the shiny side facing the bulb halfway between the bulb and your hand. You can keep your hand 2 inches from that bulb until the end of time and not get hot now. But if you wrap your hand tightly with foil and hold it 2 inches from that bulb, your hand becomes exactly like a baked potato in a short while...the foil will conduct heat to your hand and hold it in. So, my suggestion is if you want to put something on your roof to deaden noise, use some 1/8" or 1/4" solid neoprene foam that is self-adhesive (like Kevin mentioned). Then when you install the headliner, lay that fiberglass on top so that it does not touch the roof with the foil side facing upward. You'll get some sound deadening plus some heat protection. Some people used to call rockwool insulation gray fleece back when it was used in residential construction. Trust me, the only place you want that in any pickup is in the bed being taken to the dump.
