To bake or roast means to cook by dry heat. The oven temperature should be high enough to keep the moisture evaporated from the oven as it collects, otherwise a steamed roast is the result. But, the temperature should not be so high as to cook the roast too fast and cause it to dry out.
Put a roast into a hot oven (425–475 degrees). Then reduce the heat as the roast warms. The theory in back of this is simple: there is more condensation at the time the cool roast enters the oven than when it becomes warm. As the food warms, the heat is gradually reduced to about 325 degrees. Cooking temperatures are but approximations. You must know your stove and the food you are cooking, and adjust the temperature accordingly.