Soak the white beans for 24 hours or overnight, or use 500 g of canned cooked white beans.
Cook the beans in plenty of water until tender. Drain, reserving 1,5 cups of the cooking water.
While the beans cook, preheat the oven to 180 °C (356 °F). In a bowl, mix the butternut squash, red bell peppers, carrots, thyme, rosemary, cumin, 1/2 tsp of salt, and 2 tbsp of olive oil. Toss well, spread on a baking sheet, and roast in the oven for about 40 minutes.
Heat 2 tbsp of olive oil in a pot over medium heat. Add the bay leaf and onion, sauté for 5 minutes. Add garlic and sauté for 1 more minute.
Stir in the tomato paste and mix it well with the onion and garlic, letting it meld together as it heats.
Add the diced tomatoes, 1/2 tsp of salt, and balsamic vinegar. Cover and cook on low heat for 4 minutes.
Add the roasted vegetables to the pot, followed by the cooked beans and the bean cooking water (or water). Season with black pepper and adjust the salt. Stir well and cook for 30-40 minutes, until thickened and the flavors have melded.
Turn off the heat, stir in fresh parsley, and let the stew rest for 5–10 minutes before serving.