Combine undrained pineapple, oregano and garlic powder in shallow, nonmetallic dish.
Add chicken, turn to coat all sides; cover and marinate 15 minutes in refrigerator.
Grill or broil chicken and pineapple, brushing with reserved marinade, 5 to 8 minutes on each side or until chicken is no longer pink in center and pineapple is golden brown; discard any remaining marinade.
Combine salad dressing, water chestnuts (or jicama) and bell pepper; spread onto bottom halves of rolls.
Top with chicken, bell pepper rings and pineapple and top halves of rolls; garnish with fresh fruit and mint leaves, if desired.