Preheat oven to 375°.
Melt butter in a large nonstick skillet over medium-high heat. Add onion and bell pepper; sauté 5 minutes or until tender. Stir in black pepper.
Divide onion mixture and turkey evenly among bottom halves of rolls; top each serving with 1 cheese slice. Cover with top halves of rolls.
Place sandwiches on a baking sheet. Bake at 375° for 5 minutes or until cheese melts.