Bring rice and water to a boil in a saucepan. Reduce heat to medium-low, cover, and simmer until rice is tender and the liquid has been absorbed, 20 to 25 minutes.
Mix tomatoes, vinegar, garlic, cumin, chili powder, salt, oregano, and black pepper together in a bowl.
Whisk oil into tomato mixture to make a dressing.
Stir rice, black beans, and corn together in a bowl; toss with dressing until well-coated.