Preheat the oven to 425°F.
Add the vegetables, sliced onion and rosemary sprig to a large parchment-lined baking sheet. Drizzle avocado oil on top. Place in the middle of the oven and roast for 30-35 minutes until the edges are crispy and veg is fork tender.
When there is 10 minutes left of cooking for the root veggies, combine the tomatoes, beans and spinach in a large saucepan on the stovetop over medium to high heat. Use a wooden spoon to break the frozen spinach apart. Stir often for about 6-8 minutes.
When the veggies are done roasting, add them into the saucepan. Top with oregano. Let everything simmer for 5 minutes.
Remove from hear. Taste and season with salt and pepper as needed and enjoy.