Cut the eggplant and zucchini into your desired size of cubes and the bell pepper and red onion into chunks. Put the vegetables in an oven dish and toss them in olive oil, salt and pepper.
Preheat the oven and put the veggies inside for 15 minutes (200ºC or 400ºF).
Cook the spaghetti according to package instructions until it's al dente (8-10 minutes). Put salt in the water. Drain and set aside until use.
Cut the mushrooms in slices. Heat oil and unsalted butter over medium-high heat in a large skillet. Add in mushrooms and cook for a few minutes until it's lightly browned.
Add 3 tbsp miso paste and some pasta water into the skillet and stir till mushrooms are covered in sauce.
Add the spaghetti and roasted vegetables and toss it well with the sauce.
Garnish with parmesan cheese and parsley.
Notities
For a creamy sauce, you can mix the cheese with the sauce before adding the pasta.
You can also use white spaghetti or another type of pasta.