Cook pasta according to packet instructions, drain and set aside.
Place broccoli and butternut in an oven-proof dish. Sprinkle with olive oil, salt and pepper and roast for 30-40 minutes until soft and caramelized.
While veggies are grilling, make the white sauce: Sift flour into cold milk and whisk until combined. Transfer to a pot and bring to a boil. Turn down the heat, add the sundried tomatoes’ oil and whisk continuously over very low heat until thick and lump-free. Add salt and pepper to taste. If your white-sauce becomes lumpy, transfer it to a food processor and mix until smooth and velvety.
Add the pasta and chopped sundried tomatoes to the dish with vegetables. Mix to evenly spread the ingredients.
Pour over the white sauce and mix.
Top with an even layer of breadcrumbs and bake for about 30 minutes.
Cut into squares and serve with a squirt of Sriracha and fresh parsley.