Place 4 large chicken breasts on a slow cooker.
In a small bowl, mix together the ingredients to make the fajita seasoning mix.
Sprinkle seasoning over both sides of the chicken breasts in the slow cooker.
Add the sliced onions and red and green bell peppers on top of the chicken.
Pour in the tomato sauce, lime juice, chipotle chiles, and diced tomatoes and chiles.
Cook on high for 4 hours or low for 6 - 8 hours. Using two forks, shred the chicken breasts and stir thoroughly in the slow cooker.
In a 9 x 13 baking pan, place the bottom half of the rolls, cut side up, into the bottom of the pan.
Layer the Chipotle Lime Fajita Chicken and vegetables on top of the rolls.
Then place the slices of cheese on top of the chicken to cover everything.
Then top with the other half of the rolls.
In a small bowl, stir together the melted butter, dijon mustard, Worcestershire, and minced garlic.
Brush on the melted butter mixture on top of the rolls.
Bake for 15 to 20 minutes or until cheese is melted.