Get your oven hot to 425°F (218°C) and line two baking sheets for easy cleanup.
In a big bowl, gently toss your cauliflower florets with 1/4 cup of olive oil, sea salt, and black pepper until well coated.
Spread the seasoned cauliflower out evenly in a single layer on your prepared baking sheets. Roast for about 25 minutes until the florets are beautifully browned and tender. If your sheets don't fit side-by-side, remember to rotate them halfway through!
While the cauliflower roasts, warm the remaining 1 tablespoon of olive oil in a skillet (a cast iron one works great!) over medium-high heat.
Add the Italian sausage and cook, breaking it up with a spatula, for 8-10 minutes until it's nicely cooked through and browned.
Push the sausage to one side of the skillet, add the minced garlic to the cleared space, and sauté for about a minute until it smells wonderfully fragrant. Stir the garlic into the sausage.
Pour in the marinara sauce and Italian seasoning. Let it simmer gently for 2-3 minutes until the sauce is rich and bubbly. Taste and adjust salt and pepper if you like.
Once the cauliflower is ready, lower your oven temperature to 400°F (204°C).
In a 9x13 inch baking dish, arrange half of the roasted cauliflower florets in an even layer.
Dollop half of the creamy ricotta cheese evenly over the cauliflower, then sprinkle with half of the shredded Parmesan cheese.
Next, spread half of the savory sausage marinara evenly over the cheese layers.
Finally, sprinkle with half of the shredded mozzarella cheese.
Repeat these delicious layers with the remaining cauliflower, ricotta, Parmesan, sausage marinara, and mozzarella.
Bake your cauliflower ziti in the preheated oven for 10-15 minutes, or until the cheese is wonderfully melted and turns a beautiful golden brown. Serve hot and enjoy!