Heat the olive oil in a skillet over medium heat. Add the diced onion and sauté for about 5 minutes until softened.
Stir in the minced garlic and cook for an additional minute until fragrant.
Transfer the sautéed onion and garlic to the crockpot.
Pour in the vegetable broth and add the diced tomatoes, cream cheese, Italian seasoning, salt, and black pepper. Stir to combine.
Cover and cook on low for 4 hours or on high for 2 hours, stirring occasionally.
After the cooking time, add the tortellini and chopped spinach to the crockpot.
Cover and cook for an additional 30 minutes on high, or until the tortellini is tender.
Before serving, stir in the grated Parmesan cheese until melted and well combined.