Place the two slices of smoked salmon onto two sheets of cling film. Place the rocket on top, squeeze over the lemon juice and drizzle with olive oil. Season with freshly ground black pepper and roll up. Remove the cling film and place the smoked salmon rolls on a serving plate.
For the potato crisps, place the vegetable oil into a deep, heavy-bottomed pan and heat until a small cube of bread sizzles and turns golden when dropped into it. (CAUTION: hot oil can be dangerous. Do not leave unattended.)
Carefully place the potato slices into the hot oil and deep fry for 1-2 minutes, or until golden-brown and crisp. Remove from the oil with a slotted spoon, drain on kitchen paper and sprinkle with sea salt.
To serve, place the potato crisps on the serving plate with the smoked salmon rolls and garnish with lemon wedges and dill sprigs.