Preheat oven to 375°F (190°C). In a bowl, mix softened cream cheese, sour cream (or Greek yogurt), and ranch (or blue cheese dressing) until smooth.
Stir in shredded chicken, buffalo sauce, 3/4 cup shredded cheese, garlic powder, salt, and pepper. Taste and adjust buffalo sauce for spice level.
Spread the mixture in a small baking dish. Top with remaining cheese and crumbled blue cheese if using. Bake 12–15 minutes until bubbly and slightly golden.
Split slider rolls and toast cut-side up for 3–4 minutes. Brush insides with melted butter mixed with garlic powder.
Spoon a generous tablespoon (or more) of hot dip onto each bottom roll, place tops on, sprinkle with chopped celery or green onion, and serve warm.
Notes
Make-ahead: Prepare the dip (uncooked) and refrigerate up to 24 hours; bake just before serving.
Substitutions: Use Greek yogurt for part of the cream cheese to lighten the dip.
Vegetarian option: Substitute shredded jackfruit or cooked chickpeas for the chicken.