Preheat oven to 300°F (150°C).

Place tomatoes in an even layer on a baking sheet. Drizzle with oil, and sprinkle with oregano, red pepper, salt, and black pepper.

Roast tomatoes until blistered and very soft, 40 to 45 minutes. Transfer to a medium bowl, and let cool completely.

Add mozzarella pearls to tomatoes, tossing to combine.