Place the chicken cubes in a large zip bag. Add lemon zest and juice, garlic, rosemary, olive oil, salt, and red pepper flakes to the bag. Turn the bag a few times to mix the marinade and work it into the chicken. Marinate the chicken in the bag for at least 1 hour (no more than 2) Keep refrigerated.
Drain the marinade from the chicken, and then string the chicken onto skewers, adding in a couple of lemon wedges to each skewer.
Bring the grill to medium heat and cook the skewers directly over the heat for 6 to 8 minutes, rotating the skewers as you go to ensure even cooking.
Once the chicken is cooked through, transfer it to a platter and allow to cool before serving. Use the grilled lemon wedges to squeeze onto individual servings.
