Heat oven to gas 6, 200°C, fan 180°C. Whisk together the vinegar, half the pesto, the oregano, a pinch of salt and some fresh black pepper in a large bowl. Add the peppers, tomatoes and mushrooms with half the basil leaves. Toss to coat, then tip into a roasting tray and cook for 30 minutes, shaking half-way through. Meanwhile make the batter. Tip the flour and bicarbonate of soda into a mixing bowl with ½ teaspoon of salt and some black pepper. Make a well in the centre and add the eggs, remaining pesto and buttermilk. Whisk until you have a thick, lump-free batter. Heat some sunflower oil in a large frying pan. Add 3 tablespoons batter to the pan and cook on a medium heat until bubbles appear on the surface, then carefully flip over and cook for another minute or so until golden on both sides. (You should be able to cook 2 pancakes at a time in this way.) Remove and continue cooking until you have used up all the batter, keeping any cooked pancakes warm in the oven. Serve the pancakes in stacks with the roasted vegetables. Scatter over the rocket and leftover basil. Drizzle over any leftover dressing from the tray and serve immediately.