Preheat the oven to 350°F (177°C).
In a large 12-inch non-stick skillet over medium-high heat, cook 1½ lb ground beef until no longer pink, breaking it up with a meat masher or spatula.
Drain any excess grease from the skillet, then add 1 (1-oz) packet taco seasoning and 1 cup salsa; cook about 5 minutes until most liquid is absorbed.
Remove the skillet from heat and stir in the 8 oz cubed Velveeta until the cheese melts and is fully combined with the meat.
Using a serrated knife, slice the entire loaf of Hawaiian rolls horizontally, keeping the loaf intact; place the bottom half in a sprayed 9×13-inch baking dish.
Spread the beef and Velveeta mixture evenly over the bottom buns, then sprinkle 1 cup shredded cheddar cheese over the meat. Top with the top half of the rolls.
In a small bowl, mix 2 Tbsp melted butter with 1 tsp taco seasoning and brush the seasoned butter evenly over the top of the rolls.
Bake for 20–25 minutes, until the tops are golden brown and the sliders are heated through.
Remove from the oven and sprinkle with dried parsley if desired, then slice between servings to separate sliders.