Preheat your grill to medium-high heat.
Place the chicken breasts on the grill and cook for 6-8 minutes per side, or until they are cooked through.
While the chicken is cooking, heat the buffalo sauce in a small saucepan over low heat.
Once the chicken is cooked, transfer it to a cutting board and use two forks to shred it into small pieces.
Transfer the shredded chicken to a bowl and toss it with the buffalo sauce until it is evenly coated.
Warm the tortillas in the microwave or on a dry skillet over medium heat.
To assemble the tacos, place a small handful of the buffalo chicken onto the center of each tortilla. Top with diced tomatoes, shredded lettuce, and a drizzle of ranch dressing.
Roll up the tortillas tightly and serve immediately.