Fresh Vegetable Pizza

2 (8-oz.) cans Pillsbury Refrigerated Crescent Dinner Rolls
1 (8-oz.) carton dairy sour cream
1 to 2 tablespoons prepared horseradish
1/4 teaspoon salt
1/8 teaspoon pepper
2 cups fresh mushrooms, chopped
1 cup chopped, seeded tomatoes
1 cup small broccoli florets
1/2 cup chopped green bell pepper
1/2 cup chopped green onions

Heat oven to 375 F. Separate dough into 4 long rectangles. Place rectangles crosswise in ungreased 15x10x1-inch baking pan; press over bottom and 1-inch up sides to form crust. Seal perforations. Bake at 375 F. for 14 to 19 minutes or until golden brown. Cool completely. In small bowl, combine sour cream, horseradish, salt and pepper; blend until smooth. Spread evenly over cooled crust. Top with remaining ingredients. Cut into appetizer-sized pieces. Store in refrigerator.