Place the chicken breasts into the dish of a slow cooker. Pour the buffalo sauce over the chicken, and stir to combine. Cover and cook on low for 7 to 8 hours or high for 4 to 5 hours.
Shred:
Once the chicken is cooked through, shred the meat with two forks and toss to coat with the sauce.
Serve:
Prior to serving, warm the tortillas.
To assemble, place shredded lettuce onto a tortilla, top with buffalo chicken, a drizzle of ranch, and blue cheese crumbles.