In a medium mixing bowl, combine the softened cream cheese, Buffalo wing sauce, Greek yogurt, garlic powder, and black pepper. Stir until smooth and creamy.
Add the shredded cooked chicken, crumbled blue cheese, and sliced green onions to the bowl. Fold together until the chicken is evenly coated in the creamy buffalo mixture.
Trim both ends off the English cucumbers. Using a mandoline slicer or wide Y-peeler, slice the cucumbers lengthwise into long, thin, flexible ribbons (about 1/16-inch thick). Discard the outer skin-only strips.
Lay the cucumber ribbons flat in a single layer on a double layer of paper towels. Gently press the tops with another paper towel to absorb excess surface moisture.
Place a rounded tablespoon of the buffalo chicken filling at one end of each cucumber ribbon.
Roll the cucumber ribbon tightly around the filling from one end to the other to create a compact roll-up.
Stand the cucumber rolls upright or lay them seam-side down on a serving platter. Drizzle with extra buffalo sauce and ranch dressing, and garnish with extra sliced green onions before serving.