Preheat the oven to 200 degrees C. Halve the onion lengthways, then cut into thin wedges. Place in a large plastic bag with the garlic, capsicum chunks, fennel or celery, zucchini slices and oil. Toss together well, then tip out into a shallow ovenproof dish. Alternatively, you can mix everything together in a large bowl before tipping into the ovenproof dish.
Add the artichoke hearts to the vegetables, being careful not to break them up too much, then season with freshly ground black pepper. Sprinkle the oregano, paprika or chilli, and cumin over the vegetables, then transfer to the oven and roast for 15 minutes.
Stir in the tomatoes with their juice, and the drained beans. Return the vegetables to the oven to bake for a further 10 minutes.
Meanwhile, stir the ricotta with the milk, to thin it to a thick cream. Drizzle the cheesy sauce over the vegetables. Mix the grated cheese and breadcrumbs together and scatter on top. Return to the oven to bake for a further 15 minutes until golden and bubbling.