Once your tomatoes are in the pan, wash your hands to get the oil off your fingers before you move onto the spices and seasoning. You can experiment with spices, but good ones to start with are: rosemary, oregano, black cracked pepper (not whole), sea salt, and basil. These all go great with roasted tomatoes for a Mediterranean-style meal, but maybe another time you could try some chilli for a different flavor.

Summary:
Prepare your spices.