Preheat oven to 425°F.
To roast garlic, cut the top off the whole bulbs to expose cloves. Dress with a little EVOO and season with salt and pepper (fresh rosemary or thyme sprigs make tasty roasting companions as well). Wrap tightly in foil and roast until tender and light caramel in color, about 45-60 minutes. Let cool.
In a medium bowl, mix ricotta with lemon zest, pepper flakes, thyme 1/2 cup of Parmigiano-Reggiano, salt and pepper.
Arrange pizza crusts on 2 rimmed baking sheets. Spread roasted garlic on the cut side of the bread and top with ricotta mixture then sprinkle with the rest of the Parmigiano-Reggiano and fresh mozzarella. Bake to golden, 12-15 minutes.