@boomerang,
Most non-stick materials can't be used above temperatures above 400 degrees without emitting toxic fumes.
Using cooling racks in a sheet-pan for roasting items in the oven is a common practice in the food industry.
If you are in doubt about the materials, don't use it. Better to err on the safe side.
Some alternatives:
If you are roasting something like meat, you can use a layer of root vegetables below the meat to lift the meat up off the floor of the pan. Another thing people sometimes use are the burners from a gas stove, just wrap them in foil. You might also consider placing the item directly on the rack of your oven and place a pan under it on the shelf below to catch drippings. If you have a toaster oven, consider using one of the racks from that oven in a sheet pan. If you have some of the Ball lids used for canning, you can fill the floor of a sheet pan with them before placing your item on them.