Cook the linguine in a large pot of well-salted water according to package directions. During the final 5 minutes of cooking, add the frozen edamame and shredded carrots directly to the pot with the pasta.
Before draining, reserve about 1/2 cup (480 ml) of the starchy pasta water.
Drain the linguine and vegetable mixture well and return it to the hot pot.
Pour the Alfredo sauce over the pasta and add the snipped fresh rosemary.
Stir gently over low heat until the sauce is warmed through and coats everything beautifully. If the sauce is too thick, add a splash of the reserved pasta water to reach your desired consistency.
Season with salt and pepper to taste and serve immediately.
Don't boil the Alfredo sauce.
When combining everything in the final step, use low heat and stir gently just until the sauce is heated through.
Boiling a cream-based sauce can cause it to separate.