Preheat the oven to 180C. Cut the pumpkin open and remove all the seeds. Cut into 2cm slices and spread them on a baking sheet lined with baking paper. Sprinkle over all the other ingredients except the grapefruit and toss well with the olive oil. Roast in the oven for 30 minutes or until soft. Remove from the oven and cool slightly. Peel and slice your grapefruit, removing all pips, then scatter the slices over the squash.
Place all the salsa verde ingredients in a food processor and blitz together until the sauce reaches a pesto-like consistency. Spoon over the roasted squash and grapefruit.