Preheat the oven to 200°C. Cut the new potatoes into bite-sized pieces and the cauliflower into florets. Cut the aubergine, courgette, and sweet pepper into chunks. Slice the onion and finely chop the garlic, chilli, and oregano.
Toss the potatoes and aubergine with olive oil, salt, and pepper.
Arrange in a baking dish and roast in the oven for 20 minutes.
While the vegetables are roasting, heat a little olive oil in a pan over medium heat. Sauté the onion and garlic until softened. Add the tin of chopped tomatoes and diced chilli pepper and stir to combine.
Add the fresh spinach and chopped oregano to the sauce and cook until the spinach is wilted. Season with salt and pepper to taste.
After 15 minutes, remove the baking dish from the oven and add cauliflower, courgette, and sweet pepper. Toss with the other vegetables, return the baking dish to the oven and roast for an additional 15-20 minutes, or until all vegetables are tender.
Pour the spinach and tomato sauce over the roasted vegetables (or serve with the tomato sauce on the side).
Return to the oven for 5-10 minutes, or until the sauce is heated through and bubbling. To serve, sprinkle with some chopped oregano.