Are there reasons to use olive oil when roasting food at high temperatures?
Just because the oven is reaching high heat does not mean the olive oil that is on the surface of what is being cooked will reach the oven temperature (or get past the smoke point, even). In a deep fryer, heat is transferred almost directly from the heating element to the oil. In a pan, heat is transferred from the heat source to a pan, then directly to the oil. Both those represent very efficient heat transfers, and can bring an oil to past its smoke point. The oven transfers heat from source to food via the air, which is a very inefficient form of heat transfer. The temperature of the oil you apply to your food will be vastly more affected by the mass of the food than by the air in the oven environment.