Place garlic in a small stainless steel bowl; drizzle with 1 tablespoon olive oil and cover with aluminum foil.
Bake in the preheated oven until tender and browned, about 1 hour. Remove and chop garlic. Increase oven temperature to 375 degrees F (190 degrees C).
Grease a 10x12-inch pan with the remaining olive oil; sprinkle lightly with garlic salt. Place crust onto the pan.
Mix spinach, mayonnaise, and Parmesan cheese together in a bowl. Spread mixture over the pizza crust.
Sprinkle chopped roasted garlic along the edges of the crust. Cover with 1/2 the Italian cheese blend. Add lobster and shrimp. Sprinkle on onions on top and the remaining Italian cheese blend. Finish with olives. Drizzle with the remaining oil; sprinkle seafood seasoning, salt, and pepper on top.
Bake in the preheated oven until crust is golden brown and lobster and shrimp are opaque, 10 to 12 minutes.