Grill the peppers, skin-side up, under a preheated moderate grill, until blackened. Place in a freezer bag and allow to cool slightly, then peel off the skins and chop the peppers into small pieces.
In a small bowl, whisk together the oil and vinegar, season to taste, then stir into the peppers.
Sprinkle the paprika on both sides of the halloumi slices. Lightly brush a griddle pan with oil and heat over a high heat. Add the cheese and griddle for 1-2 minutes each side, until lightly charred and starting to melt. Remove from the heat and squeeze over the lemon juice.
Toast the pitta, then cut into strips. Divide the rocket leaves between four plates, arrange the peppers on top, followed by the halloumi, and sprinkle with the pine nuts. Serve immediately with the pitta.