Taco Meat → Enchiladas
See my Freezer Meal Enchildadas to see how I transform leftover taco meat into enchiladas. I've done this with ground beef, ground turkey, and shredded chicken.
Salmon → Salmon Cakes
I roast salmon fillets at least once a week, and then freeze the leftovers. You can use this recipe for Salmon Patties as a starting point, if you don't already have one. Another favorite nextover is salmon korokke (Japanese croquettes), but I find the breading and frying too much work to do this often.
Roast Beef → Beef Hash or Pot Pie
This Serious Eats Roast Beef Hash recipe is a favorite around here. I don't have a favorite pot pie recipe, because I just make a roux-based white sauce, add meat and veggies, top with puff pastry or biscuits, and bake until the topping is done.
Roasted Veggies → Frittata
Use my Bacon & Zucchini Frittata or Potato & Broccoli Spanish Tortilla recipes as a starting point.
Any Meat → Fried Rice
I make fried rice once a week, using leftover roast beef, salmon, kalua pork, or sometimes even Spam. (Yes, that's a nod to my Hawaii roots.) I use soy sauce and sriracha to taste for seasonings (along with a decent amount of avocado oil and sesame oil), but if you'd like a recipe, try this Chicken Fried Rice, and use whatever veggies you have on hand.
What are your favorite nextovers?