Heat oven to 190°C and line a 23x32cm Swiss roll tin with baking paper.
Wash spinach, wild garlic, and nettles thoroughly after removing stalks.
Boil leaves in a heavy-based saucepan for 3 minutes until limp.
Drain leaves and press through a sieve twice to remove all liquid.
Fry shallots in olive oil until translucent and stir in seasonings.
Puree cooked leaves, egg yolks, and shallot mixture in a food processor.
Whisk egg whites to stiff peaks and fold into the spinach puree.
Spread mixture into tin and bake for 12 minutes until firm.
Turn out onto a work surface and peel off baking paper.
Whisk egg yolks, lemon, mustard, vinegar, and olive oil for mayonnaise.
Drizzle in sunflower oil slowly while whisking until thickened.
Fold shrimp into the mayonnaise and season.
Spread filling over the roulade and roll up from the short end.
Rest for 30 minutes, slice thickly, and garnish with flowers.