In a large skillet, heat the olive oil over medium heat. Add the Italian sausage and cook until browned, breaking it apart with a spoon, about 5-7 minutes. Transfer the sausage to a slow cooker.
In the same skillet, add the onion and garlic. Sauté for 2-3 minutes until the onion is translucent. Add the carrots, celery, red bell pepper, and zucchini. Cook for another 5 minutes, then transfer the vegetables to the slow cooker.
Pour in the diced tomatoes and chicken broth. Stir in the oregano, thyme, paprika, salt, and pepper. Mix everything well.
Cover the slow cooker and cook on low for 6-8 hours or on high for 3-4 hours, until the vegetables are tender and the flavors meld together.
About 15 minutes before serving, stir in the frozen peas and let them heat through.
Serve hot, garnished with fresh parsley.