Begin by boiling a large pot of water. Carefully add the cabbage head and cook for about 5-7 minutes until the outer leaves are tender. Remove the cabbage from the water and let it cool. Peel off 12 large leaves and set aside.
In a skillet, heat the olive oil over medium heat. Add the diced onion and garlic, sautéing until the onion is translucent, about 5 minutes. Remove from heat and let cool slightly.
In a large mixing bowl, combine the ground meat, cooked rice, sautéed onion and garlic, salt, pepper, paprika, and thyme. Mix well until fully combined.
Take a cabbage leaf and place about 2-3 tablespoons of the filling at the stem end of the leaf. Fold the sides over the filling and roll from the stem end to the tip, securing the filling inside. Repeat this process for all cabbage leaves.
Preheat your oven to 350°F (175°C). In a baking dish, pour half of the tomato sauce on the bottom. Arrange the stuffed cabbage rolls seam-side down in a single layer on top of the sauce. Pour the remaining tomato sauce and diced tomatoes over the top.
Cover the baking dish with aluminum foil (if desired) and bake in the preheated oven for 45 minutes. Remove the foil and bake for an additional 15 minutes to let the rolls brown slightly.
Once cooked, remove from the oven and let sit for a few minutes before serving. Garnish with fresh parsley if desired.