Wrap garlic heads in foil and place on small rimmed baking pan. Transfer to oven and cook 1 hour or until garlic is dark golden brown and very soft. Remove from oven and let stand for 5 minutes or until cool enough to touch. Squeeze garlic cloves from their skin into a small bowl.
Preheat grill for two-zone grilling: half of grill should be set to medium-high; other half should be off (indirect heat).
Stretch and shape dough into 14-inch circle and place on pizza pan or large tray. Brush one side of dough with 1 tablespoon oil. Use hands to transfer dough to direct heat side of grill, oiled side down. Do not worry if dough becomes a little misshapen during the transfer. Cook 2 minutes, or until the dough releases itself from the grates (do not disturb dough before it releases).
Brush top side of dough with remaining 1 tablespoon oil, then use tongs to flip dough. Cook 2 minutes or until dough releases from grates. Continue cooking dough 3 to 4 minutes longer or until dough is firm and grill-marked in all areas, flipping and rotating frequently but keeping grill closed when not flipping.
Remove dough from grill and spread with sauce. Top with chicken, Stella® Mozzarella Cheese, everything bagel seasoning, and roasted garlic cloves.
Transfer pizza back to grill on indirect heat side. Close grill and cook 8 to 10 minutes or until toppings are warmed through and crust is fully cooked.
Remove pizza from grill and top with spinach. Cut and serve immediately.