Start by preheating your oven to 425 degrees F. Toss the red onion, aubergine, red bell pepper, yellow bell pepper, courgettes, and garlic with olive oil, harissa, thyme, salt, and pepper on a baking tray. Roast in the preheated oven for about 25 minutes, or until the vegetables are caramelized and fragrant. Keep an eye on them to prevent burning.
Boil some water in a saucepan and add the rigatoni. Stir occasionally and cook until just al dente, about 8-10 minutes. The pasta should be firm yet tender when you bite into it. Avoid overcooking, as mushy pasta will not mix well with the roasted vegetables.
Once the pasta is cooked, drain it, but save some of the starchy pasta water. Combine the pasta with the roasted veggies, then add the lemon juice and goat's cheese. If it feels dry, stir in a splash of reserved pasta water to achieve a creamy consistency. Make sure everything is well coated.
Stir in some chopped parsley and toasted pine nuts. Gently mix to maintain the integrity of the goat's cheese.
Portion the pasta onto plates and top with a little more parsley for added color. Check and adjust the seasoning as necessary.