Cook rotini to desired doneness as directed on package. Drain; cover to keep warm.
Meanwhile, in large saucepan, cook vegetables as directed on package until crisp-tender. Drain well; return to saucepan. Stir in Alfredo sauce; cook and stir over medium-low heat until smooth.
Gently stir tuna and pepper into vegetable mixture in saucepan; cook until mixture is hot.
Serve vegetable mixture over rotini.