For the Sauce: If using already prepared pizza sauce, skip this step.
Pour juice from jar of tomatoes into a saucepan and bring to a simmer. Add the tomato paste, sugar, oregano, crushed red pepper, and thyme sprigs and continue to simmer for 10-15 minutes, or until sauce thickens.
Taste and adjust herbs, spice, and sugar, as desired. When sauce is done, remove from heat and set aside until ready to top pizza.
For the Toppings:
Warm oil or butter over medium heat in a medium sized skillet. Sauté mushrooms with garlic in the butter long enough to allow mushrooms to release moisture and soften, about 5 minutes.
Remove mushrooms from the skillet and add the zucchini rounds to the same pan. Cook over medium heat until zucchini softens slightly and lightly brown in some spots (it is okay if the pan seems dry, that will help the zucchini brown a little).
When done, remove zucchini from skillet and set aside until ready to top pizza.
For the Crust:
Preheat oven to 450° and position rack in the lower third of the oven.
Using a box grater, shred fresh cauliflower until you have a little more than 2 cups (it will shrink as the moisture evaporates). Spread cauliflower in the bottom of a dry cast iron skillet and cook on medium heat for 6-8 minutes, stirring frequently, as cauliflower moisture evaporates.
Cauliflower will lightly roast and turn light brown in spots, but that is okay. Pour cauliflower out of skillet onto paper towels and let cool. Once cooled, squeeze any additional moisture out of the cauliflower within the paper towels.
Mix cooled cauliflower, cheese, coconut flour, oregano, garlic, and salt until well blended. Stir in egg until all ingredients are combined.
Lightly brush olive oil on a non-stick pizza pan or line other types of pizza pans with parchment paper. With fingertips, press crust mix out on pan to form a 9"-11" crust. (Size can vary.) Trim the parchment to about 1-inch around crust.
Place crust in the oven and bake 12-15 minutes in the lower part of the oven (this will help the crust brown on the bottom), until the crust is a light golden brown.
Remove crust from oven, reposition oven rack to the middle, and turn oven on broil.
Finishing the Pizza:
Top crust with enough sauce to cover, leaving a small margin at the edge and level with the back of a spoon. Add as much sauce as you prefer—a thin layer or a thick, saucy base works too.
Spread 3/4 to 1 cup of mozzarella cheese on top of the sauce and then layer the remaining vegetables so that each slice will have a nice combination of each.
(It's okay if you have vegetables left over, use them to make an omelet the next day.) Top with the basil, Romano cheese and a drizzle of olive oil.
Return pizza to the oven and broil to melt cheese and meld flavors. Remove from oven once top starts to lightly brown and edges of crust are golden brown.
Slice and serve from the pan unless using parchment paper. If using parchment, allow pizza to rest 2-3 minutes, then slide onto a cutting board. Gently roll parchment paper under toward cutting board to remove it from under the pizza and discard. Slice pizza and serve.
The amounts in the ingredient list for the toppings is approximate, each one can be adjusted based on preference.