Preheat the oven to 220°C, fan 200°C, gas 7. Tip the potatoes into a large roasting tin. Add the oil, season, toss and spread in a single layer. Scatter over the pancetta. Roast for 20 minutes until tender and golden.
Meanwhile, for the gremolata topping, whiz the bread in a food processor. Add the pesto, almonds and parsley; whiz until chopped. Tip into a bowl; add the lemon zest and season.
Press the gremolata topping on to the salmon. After the potatoes have roasted for 20 minutes, add the asparagus to the tin, then place the salmon on top. Return to the oven for 12-15 minutes until the salmon is cooked through.