Combine pasta, tomatoes, onion, garlic, red-pepper flakes, basil, oil, 1 tsp kosher salt, 1/4 tsp pepper, stock and water in a large straight-sided skillet.
Bring to a boil over high heat. Boil mixture, stirring and turning pasta frequently with tongs, until pasta is al dente, about 9 minutes.
If there is too much liquid remaining, add flour until sauce thickens
Add rocket, stir until it wilts
Season to taste with salt and pepper, divide among 4 bowls, and garnish with basil. Serve with oil and Parmesan.