MAKE THE TOMATO SAUCE: Heat the olive oil in a medium heavy-bottomed pot over medium-high heat. Add the onion and garlic and cook until softened, 5 to 6 minutes. Add the thyme and oregano, and season with salt during the last minute of cooking. Add the tomatoes and stir to combine. Fill the tomato can with 1 cup water and add it to the pot. Simmer for 25 minutes. Using an immersion blender, blend the sauce until almost smooth. Season with salt and pepper as needed and stir in the basil right before serving.
MAKE THE MEATBALLS: Heat a small sauté pan over medium-high heat and add 1 tablespoon of olive oil. Add the onion and garlic and cook until softened, about 4 to 5 minutes. Add the thyme and oregano and cook for 1 minute more. Transfer to a bowl and cool completely.
In a large bowl, mix the ground beef, raisins, pine nuts, breadcrumbs, Pecorino Romano, egg and the cooled onion mixture until just combined. Season with salt and pepper. Roll into 1½-inch meatballs. (The recipe should make about 16.)
Heat the remaining 2 tablespoons of olive oil in a large sauté pan over medium-high heat. Add the meatballs and sear on all sides until golden brown, 6 to 8 minutes. Place the meatballs in the tomato sauce and simmer until cooked through, 13 to 15 minutes.
MAKE THE POLENTA: Bring 4 cups of salted water to a boil. Gradually whisk in the polenta and simmer until thick and creamy, according to package instructions.
Once thickened, remove from heat and stir in the Pecorino. Season to taste with salt and pepper. Serve the meatballs atop the polenta. Garnish with additional Pecorino, parsley and raisins.