Place chicken breasts, marinara sauce, chicken broth, oregano, garlic powder, salt, and pepper into the slow cooker.
Cover and cook on high for 4 hours or low for 7 hours until chicken is tender.
Remove chicken from the slow cooker and shred using two forks then return the shredded chicken to the pot.
Stir in the dry rotini pasta into the liquid.
Cover and cook on high for an additional 20 to 30 minutes until the pasta is al dente.
Stir in the mozzarella and parmesan cheese until fully melted and incorporated into the broth.
Serve immediately garnished with fresh chopped basil.