HEAT oven to 400°F.
TOSS squash and red peppers with 2 Tbsp. dressing; spread onto rimmed baking sheet.
BAKE 20 to 25 min. or until crisp-tender; cool. Meanwhile, cook pasta as directed on package, omitting salt. Drain; set aside until ready to use.
MIX mayo and remaining dressing in large bowl until blended. Add pasta, roasted vegetables, 1/2 cup basil and black pepper; mix lightly. Garnish with remaining basil.