Heat milk and cream in a saucepan over medium heat until simmering, about 5 minutes. Slowly whisk in Parmesan and Romano cheeses. Remove from heat.

Whisk egg yolks together in a heat-proof bowl; slowly whisk in about 1/4 cup hot cream mixture to temper eggs. Slowly whisk egg yolk mixture into the saucepan. Season with salt and black pepper. Allow Alfredo sauce to cool; refrigerate until needed.

Whisk salad dressing, rosemary, and lemon juice together in a large glass or ceramic bowl. Add steak and toss to evenly coat. Cover the bowl with plastic wrap and marinate in the refrigerator for 4 hours.

Preheat an outdoor grill for medium heat and lightly oil the grate.

Fill a large pot with lightly salted water and bring to a rolling boil. Cook fettuccine at a boil until tender yet firm to the bite, about 8 minutes.

Heat 2 cups refrigerated Alfredo sauce in a saucepan over medium heat. Add spinach and 2 tablespoons Gorgonzola cheese.

Remove steak from marinade and shake off excess. Discard remaining marinade. Cook on the preheated grill to desired doneness, 5 to 10 minutes.