Preheat oven to 180℃. Lightly spray a small overproof dish with oil. In a bowl, combine spinach, mushrooms, peppers (if using), ricotta, egg, nutmeg and herbs.
Use a small spoon to fill cannelloni tubes with spinach mixture.
In a bowl, combine passata with ½ cup hot water. Place half in prepared ovenproof dish, with cannelloni tubes on top. Spoon any remaining spinach mix around cannelloni. Top with remaining passata.
Sprinkle with parmesan and bake for 25-30 minutes, until lightly golden.
To serve, sprinkle cannelloni with fresh basil, with rocket and cherry tomatoes on the side.