I would never freeze stuffed tomatoes; they do not hold up after defrosting. When I have extra tomatoes I always can them with great results. If you chose to try and freeze them anyway, I would cook the rice first and stuff the raw tomatoes. After defrosting slightly, I would bake them in the oven until thoroughly heated; be prepared they will not hold their shape. If you have a few extra tomatoes, quarter them and freeze them for chili or other soups; they work well like that. If you want something you can stuff and freeze, the green bell peppers are great for that.