Place bacon in a large skillet and cook over medium-high heat, stirring often, until evenly browned, about 10 minutes. Remove bacon with a slotted spoon and drain on a paper towel-lined plate. Reserve 1/4 cup of bacon drippings in the skillet.
Place asparagus, spinach, and garlic into the skillet with the bacon drippings; cook and stir over medium heat until the asparagus is tender, 8 to 10 minutes.
Sprinkle in lemon zest and toss to combine; thoroughly mix in bacon and Alfredo sauce. Reduce heat to medium-low and bring sauce to a simmer.
Fill a large pot with lightly salted water and bring to a rolling boil. Stir in rotini and return to a boil. Cook uncovered, stirring occasionally, until the pasta has cooked through but is still slightly firm, about 8 minutes. Drain well.
Transfer the rotini to a serving bowl and top with Alfredo sauce mixture.