1Heat oven to 450°F. In large shallow roasting pan, stir all three kinds of mushrooms, 3 tablespoons oil and 1/2 teaspoon of the salt. Roast uncovered 45 minutes, stirring twice, until liquid is evaporated.
2Meanwhile, in small bowl, mix vinegar, shallots, garlic, mustard, pepper and remaining 1/2 teaspoon salt with wire whisk. Slowly add 2/3 cup oil, stirring constantly with whisk. Transfer mushrooms to medium bowl; stir in 1/4 cup vinaigrette. Cool to room temperature.
3Divide spinach and radicchio among 8 salad plates; top evenly with roasted mushrooms and cheese. Drizzle with remaining dressing. Serve immediately.