Preheat the oven to 400˚F. Line 2 baking sheets with parchment paper. Toss the cauliflower florets with 1 tablespoon olive oil, 3/4 teaspoon salt, all of the paprika, and 1/4 teaspoon black pepper. Arrange the cauliflower on 1 1/2 baking sheets.
Toss the halved tomatoes and 3 ounces of oyster mushrooms in the remaining olive oil, salt and pepper. Arrange on the other half of the baking sheet with the cauliflower. Keep the vegetables separate on the baking sheet, as they will have different roasting times.
Roast the tomatoes and mushrooms for 15 minutes, remove and set aside. Roast the cauliflower for 20 minutes, or until tender and lightly browned.
In a large bowl, toss the roasted vegetables, pumpkin seeds, and spinach together. The heat of the roasted vegetables will cause the spinach to wilt. Dress with the Roasted Mushroom Vinaigrette just before serving.
Roasted Mushroom Vinaigrette
Preheat the oven to 350˚F and line a small baking sheet with parchment. Toss the mushrooms with 2 teaspoons olive oil, and lightly dust with salt and pepper. Roast for 15 minutes, or until just starting to crisp.
Add the roasted mushrooms, garlic, shallot, mushroom powder, salt, pepper, and sherry vinegar to the smallest bowl of a food processor, fitted with a metal blade. Alternatively, you can use a blender, using a small container. Whirl until the mushrooms are well chopped.
Drizzle in the olive oil, while running the food processor. If that's not possible, add it all at once and then give it a few whirls.
Dressing can be made ahead and refrigerated for up to 2 weeks.
Make this salad into a meal by adding tofu, chicken or shrimp.