Preheat the oven to 180°C, gas mark 4. Toss the pumpkin, olive oil and seasoning in a bowl, then tip onto a baking tray. Roast for 20 minutes, turning halfway, until tender.
Meanwhile, add the sugar snap peas and mangetout to a pan of boiling salted water and blanch for 1 minute. Refresh in ice cold water, drain and set aside.
Combine the fish sauce, lime juice, sugar and garlic in a large bowl. Add the sugar snaps, mangetout, onion, cucumber, spring onions and herbs. Toss, then divide between two plates. Top with the pumpkin and roasted peanuts and serve.