Preheat the oven to 450°F. Bring a large pot of salted water to a boil.
Cut the russet potatoes into ½-inch steak fries. Boil for 5 minutes, then drain and spread on a towel-lined sheet pan to dry completely for 10 minutes.
Toss the dried fries with olive oil, smoked paprika, garlic powder, and salt. Spread in a single layer on a heavy sheet pan, without crowding.
Bake for 25–30 minutes, flipping halfway through, until deeply golden and crisp on the edges.
While the fries bake, melt the butter in a saucepan over medium heat. Whisk in the flour and cook for 60 seconds until lightly toasted-smelling.
Slowly whisk in the milk and simmer until thickened enough to coat the back of a spoon, about 3–4 minutes.
Remove from heat and stir in the shredded cheddar a handful at a time until fully melted and smooth. Season with salt to taste.
Pile the hot fries onto a platter. Pour two-thirds of the cheese sauce over the fries along with half the bacon, and toss gently to coat.
Drizzle the remaining cheese sauce over the top and scatter the rest of the bacon.
Serve immediately with ranch dressing on the side.