Heat oil in heavy large skillet over medium-high heat. Add sausage and cook until no longer pink, crumbling with fork, about 5 minutes. Transfer sausage to bowl using slotted spoon. Add mushrooms to skillet and saute' 2 minutes. Add spinach and saute' until wilted. Add garlic and walnuts and stir 1 minute. Add cream and Roquefort and bring to boil. Reduce heat and simmer until thickened to sauce consistency, stirring occasionally, about 10 minutes. Add sausage and mustard. Season to taste with salt and pepper. Stir sauce until heated through.

Meanwhile, cook pasta in large pot of boiling salted water until just tender but still firm to bite, stirring occasionally. Drain. Place in large bowl. Pour sauce over pasta. Toss gently.