Preheat oven to 450°; cut off top ¼ of garlic + discard; place garlic cut side up in a small baking dish; drizzle exposed cloves with 1 tsp oil + a pinch of salt; cover with foil + bake 20-25 min until soft + lightly browned; cool slightly, squeeze cloves from skins + mash with a fork

Meanwhile, chop cauliflower into 1-inch pieces, spread on a sheet pan, drizzle with 2 tbsp oil + season with salt/pep; roast 8 min, then flip veggies over + roast 5-10 min more until browned + tender

Slice 2 buns in half; toast until warm + golden; spread garlic + 2 tbsp pesto onto each bun

Divide cauliflower to toasts + serve open-faces