Cut tempeh in half crosswise; cut each half lengthwise into 6 strips. Place tempeh in a shallow dish. Combine pineapple juice, soy sauce, lime juice, cumin, oil, 1/4 teaspoon black pepper, and garlic in a small saucepan; bring to a boil. Pour pineapple juice mixture over tempeh. Marinate at room temperature 30 minutes or up to 2 hours.
Lightly coat onion and bell pepper with cooking spray; sprinkle with salt and 1/4 teaspoon black pepper. Arrange onion mixture in a wire grilling basket coated with cooking spray. Place grilling basket on grill rack; grill 5 minutes or until lightly browned, turning occasionally. Remove the tempeh from marinade, reserving marinade. Place tempeh on grill rack coated with cooking spray; grill 2 minutes on each side or until lightly browned, basting occasionally with reserved marinade.
Warm tortillas according to package directions. Arrange 3 tempeh pieces, 1/2 cup onion mixture, and 1 tablespoon salsa down center of each tortilla; roll up.