Add the chicken to the slow cooker. Pour jerk marinade over chicken. Cook on low for 6-7 hours or on high for 3-4 hours.
Peel and dice the mango. Dice the cucumber. Toss together with lime juice and salt and pepper to taste. Refrigerate until ready to serve.
When chicken is cooked, remove to a cutting board and shred. If you want it extra spicy, stir 2-4 Tbsp. of the remaining marinade into the shredded chicken.
Serve shredded chicken on rolls, topped with cucumber mango salsa.