Large chocolate manufacturers almost always source their cacao on the commodity market, paying for quantity over quality. When that cacao arrives at their processing facility, it must be carefully inspected to remove trash and other debris from farms. When farmers are paid by weight, it's not uncommon to add a bit of rocks or soil to a bag in order to get more for their cacao, so manufacturers must check for and remove such items. In small chocolate making operations— those processing less than 1-2 tons of cacao per year— cacao is often bought at a high price with a high standard of hygiene.
All cacao must be inspected to remove beans that are too small, stuck together, moldy or flat, but it generally takes less time to sort than it would if the cacao was bought at commodity prices. The cleaned cacao goes into the roaster next, where the flavors inherent in the cacao are either enhanced or covered up. Large chocolate manufacturers value consistency of flavor, so they roast all cacao at high heat to bring out a deep, bitter chocolatey flavor regardless of origin.
Most small producers take the opposite approach, roasting each cacao origin individually, at a roast temperature and length that's best suited to the characteristics of each origin. Roasting cacao brings out the flavors inherent to the beans, flavors which were previously formed during fermentation on the farm.