Preheat oven to 350°F. Spray a 9×13-inch baking dish with nonstick cooking spray.

In a large skillet over medium-high heat, cook 1½ lb ground beef until no longer pink. Drain off excess grease.

Add the entire 1 (1-oz) packet taco seasoning and 1 cup salsa to the skillet. Stir and cook about 4–5 minutes, until most of the liquid has been absorbed.

Reduce heat to low and add the cubed 8-oz package Velveeta cheese. Stir until the Velveeta is fully melted and evenly combined with the meat. Remove skillet from heat.

Using a serrated knife, slice the whole 12-oz package of Hawaiian rolls horizontally (do not separate individual rolls). Place the bottom half of the loaf in the prepared baking dish.

Spread the beef-and-Velveeta mixture evenly over the bottom half of the rolls. Sprinkle 1 cup shredded cheddar cheese evenly over the meat. Place the top half of the rolls over the cheese.

Melt 2 Tbsp butter in a small bowl or saucepan, stir in 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 filling is hot. Let the sliders rest about 5 minutes before cutting and serving.