Preheat oven to 200C/400F.
Cut cherry tomatoes into halves and slice the portobello mushrooms. Crush 4 cloves of garlic and combine everything with 1 tablespoon olive oil and 1 teaspoon balsamic vinegar. Season with some salt and pepper, and roast in oven for about 20 minutes.
While the vegetables are roasting, cook the pasta in boiling water according to package instructions. Reserve about 1/4 cup of pasta water when the pasta is done.
Combine 1/4 cup roasted pumpkin puree, 2 tablespoons coconut milk and 1 tablespoon olive oil in a bowl. Add up to 1/4 cup pasta water (a little bit at a time!) if the mixture is too paste-like (instead of sauce-like).
Tear the basil leaves into small pieces and mix it in with the drained pasta, pumpkin sauce, and roasted vegetables.
Garnish with basil leaves or pumpkin seeds if you prefer.