Prepare pasta according to package directions; drain.
Meanwhile, cook cauliflower in a large pot of boiling water until crisp-tender (about 5 minutes). Drain well; set aside.
In large skillet, heat oil over medium-high heat; add pancetta and sauté until crispy. Add in cauliflower and continue cooking until golden brown. Cool slightly.
Combine pasta with pancetta and cauliflower, Alfredo sauce, cheeses and tomato. Transfer to a greased large casserole dish. Combine bread crumbs and butter; sprinkle over pasta.
Bake in a preheated 350°F oven until golden brown and bubbly (about 35 minutes).