Whisk together ricotta cheese and milk; set aside. In a large skillet, heat oil over medium heat. Add garlic and pepper flakes; saute 1 minute. Add next 7 ingredients. Cook and stir over medium heat until vegetables are crisp-tender, about 5 minutes.
Add cheese mixture to fettuccine; top with vegetables. Toss to coat. Serve immediately.
Test Kitchen tips
This is a milder flavored dish with a spicy kick. To punch up the flavor use fresh herbs in place of dried.