Line a large baking tray with foil or parchment paper.
Place the tomatoes, olive oil and salt in a large bowl. Toss well to coat the tomatoes in the oil mixture.
Place the tomatoes cut side up on tray and sprinkle evenly with oregano and garlic. Roast the tomatoes for 2 hours or until shriveled around the edges. Remove from the oven and set aside for 10 minutes.,
To make the dressing, place the olive oil, balsamic and pesto in a small screw top jar. Shake well to combine and season with salt and pepper.
Place the spinach leaves in a large salad bowl.
Add the roasted tomatoes and parmesan.
Pour the dressing over and toss gently to combine.