Spices AND cooking process are truly what you are asking about. Using spices for such a pronounced and popular food is probably very necessary when it comes to what is usually lamb and veal. Especially the Turkish culture. They use many spices through out the majority of their foods. Without a doubt: dripping fat and vertical spit are important. However these flavors can be replicated in a standard oven with a bit of thought. Just make sure the fat stays close to the cooking meat. :)
Now I do not claim to know the exact spices nor the exact amounts. But through much research and cooking trials I have come to lean towards a certain set of spices for Döner Kebabs which will render a similar, extreme, wonderful smell and taste as your typical Döner.
I've gathered my conclusion through an extremely simple method. You simply need a preliminary understanding of the people and the area to know what spices were used. They obviously used the spices that were most readily available to them to create their recipes. SIMPLE! Of course different combinations for different dishes, but at least it'd you'd be much closer to an authentic dish this way.
Onions, Rosemary, Marjoram. Maybe some small amount of oregano, garlic, cumin, and pepper etc. TYPICAL and SIMPLY mediterranean spices. don't forget the salt! :)