Preheat over to 450 degrees f.
Cut bell peppers and parsnips into long strips. Spread over a cookie sheet, and drizzle with olive oil. Season with sea salt and black pepper. Bake for 15 minutes, until the vegetables are tender, and starting to brown around the edges.
Cook pasta per package directions. Rinse, and drain, reserving 2 tablespoons of pasta water.
Back in the pot, combine pasta, reserved pasta water, pesto, sriracha, and lemon juice. Stir until all the pasta is coated.
Add the roasted vegetables. Garnish with extra watercress leaves, pinenuts, and parmesan, if desired. Add extra sriracha (we both did!), if desired.