Preheat oven to 450°. (For a crispy crust, preheat a pizza stone on the lowest rack in the oven.)
Cook sausage in a large skillet over medium heat 6 minutes or until golden on all sides. Remove with a slotted spoon; set aside. Drain all but 1 tablespoon oil.
Add shrimp, Cajun seasoning, and garlic; sauté over medium-high heat, stirring frequently, 2 minutes or until done. Set aside.
Roll dough to 1/4-inch thickness on a lightly floured baking sheet or pizza peel. Brush edges with oil; prick with a fork. If desired, transfer crust to pizza stone dusted with cornmeal or semolina flour; bake 5 minutes.
Remove crust from oven; spread sauce to edges of crust, and top with sausage, shrimp, onion, and peppers. Sprinkle evenly with cheese. Return pizza to oven, and bake 12 minutes or until crust is golden brown and cheese melts.