Preheat oven to 400°F (200°C) and line a baking sheet with parchment paper.
Arrange zucchini rounds on the baking sheet in a single layer.
Lightly brush both sides of each zucchini round with olive oil and season with salt and pepper.
Roast the zucchini slices for 5 minutes.
Remove from oven and top each round with approximately 1 teaspoon of marinara sauce.
Distribute the shredded mozzarella cheese evenly over the marinara.
Place 2 to 3 mini pepperoni slices on each round and sprinkle with dried oregano.
Return to the oven and bake for 10 minutes or until the cheese is melted and bubbling.
Optional: Broil for 1-2 minutes for a golden brown finish on the cheese.
Serve warm.