For sauce, in a small bowl combine barbecue sauce, jalapeno pepper, and tahini. Transfer half of the sauce to another bowl for basting. Reserve remaining sauce until ready to serve. On two 8- to 10-inch skewers thread tomatillos, if using. Set aside.
Brush both sides of turkey with basting sauce. Grill turkey on the lightly greased rack of an uncovered grill directly over medium heat about 20 minutes or until the turkey is tender and no longer pink, turning and brushing once with basting sauce halfway through cooking.
Place tomatillos on grill rack next to turkey the last 8 minutes of grilling or until tender, turning once. Thinly slice turkey; chop tomatillos. Toast split rolls on the grill rack next to turkey the last 1 minute of grilling.
To serve, fill the toasted rolls with a few spinach leaves, the grilled turkey, and tomatillos or salsa verde. Spoon on the reserved sauce.