Drain, saving liquid. Cook ground lamb and onion in fat until lamb is lightly browned and onion is transparent. Pour off drippings. Add soup, vegetable liquid, vegetables, salt, and thyme. Pour into a 2-quart casserole.
Arrange tomato slices on top of mixture.
Sprinkle with salt and cheese. Bake 35-40 minutes. Add lamb and cook 3-5 minutes or until browned. Stir in rice, rosemary, salt, pepper, and lamb. Cook until thoroughly heated.