Slow Cooker Jambalaya Vegan

Name: Slow Cooker Jambalaya (Vegan)
Ingredients: 1 tablespoon olive oil, or to taste; 1 (28 ounce) can diced tomatoes with juice; 8 ounces seitan, cut into cubes; 8 ounces smoked vegan sausage, cut into 2-inch slices; 0.5 large onion, chopped; 0.5 large green bell pepper, seeded and chopped; 3 stalks celery, chopped; 1 cup vegetable broth; 2 cloves garlic, minced; 1 tablespoon miso paste; 1.5 teaspoons Cajun seasoning; 0.5 teaspoon dried thyme; 0.5 teaspoon dried oregano; 1 cup rice; 1 tablespoon chopped fresh parsley, or to taste