Rinse and dry about 1 pound firm-ripe Roma tomatoes. Slice crosswise into 1/4-inch-thick rounds and pat dry with towels. Coat a 10- by 15-inch baking pan with about 1 tablespoon olive oil. Arrange tomato slices in a single layer in pan. Sprinkle lightly with salt and pepper. Bake in a 200° regular or convection oven until tomatoes are dry but still pliable, 2 1/4 to 2 3/4 hours. While still warm, with a wide spatula, loosen slices from pan. Cool completely and store airtight in refrigerator.