Bring a large pot of boiling water to the boil and cook the tagliatelle according to the packet instructions.
Place the pesto ingredients - apart from the lemon juice - in a blender or food processor and pulse until broken down. Season to taste with lemon juice and salt.
If serving with extra pine nuts, lightly toast them in a dry frying pan for a couple of minutes. Stir often to prevent them from burning.
Once cooked drain the pasta and stir through the rocket pesto, heating gently.
Sprinkle over the toasted pine nuts and serve immediately.