Cook pasta in large saucepan as directed on package, omitting salt.
Meanwhile, heat oil in large nonstick skillet on medium heat. Add sausage and cauliflower; cook 8 to 10 min. or until cauliflower is crisp-tender and golden brown, stirring frequently.
Drain pasta, reserving 1/2 cup cooking water. Add pasta and reserved water to sausage mixture; mix lightly. Stir in VELVEETA; cook 3 min. or until completely melted, stirring frequently.