In a small saucepan, combine the hot sauce and 3 tablespoons butter and let sit over low heat to gradually melt the butter into the sauce. Set aside.
Place a medium skillet over medium-high heat; add the EVOO, 2 turns of the pan. Add the chicken and cook over high heat, breaking it up with a spoon, until cooked through and slightly browned, 6 to 8 minutes. Lower the heat, add the carrots, celery, onion and garlic and cook until softened, about 5 minutes; season with salt pepper. When the chicken is done, pour the butter mixture on top and toss to coat.
While the chicken is cooking, place another small saucepan over medium heat. Add the remaining 1 tablespoon butter. When it is almost melted, stir in the flour to make a roux. Whisk in the milk, bring to a low simmer and let bubble for 3 to 5 minutes. Turn off the heat, add the blue cheese and stir until the cheese has melted into the sauce. (The cheese will thicken upon standing, so thin out with a tablespoon of milk if necessary.)
To serve, place a couple spoonfuls of the buffalo chicken mixture on each tortilla. Top with some shredded lettuce, some tomatoes and a drizzle of the blue cheese sauce. Roll tightly and enjoy!