Step 1Beat the eggs with the parsley, dry cheese, salt and freshly ground pepper. Set aside.
Step 2Heat a large ovenproof saute pan, add olive oil and potatoes and cook over medium heat until potatoes are well browned on all sides, about 10 minutes. Add the peppers and saute until soft, about 1 minute. Add the green onions, cook until limp and then add the thyme. Sprinkle cayenne pepper over the vegetables and stir to distribute. (Turn on the broiler at this point.)
Step 3Turn up the heat under the saute pan and add the egg mixture. Immediately turn the heat down to medium low. Quickly arrange the goat cheese, cherry tomatoes and roasted garlic evenly over the surface.
Step 4Cook slowly until the edges are set. Lift the edges so that uncooked egg can run underneath, and repeat this a couple of times during the next 5 minutes or so. Peek underneath and make sure the bottom isn't browning too quickly; if it is, reduce the heat.
Step 5When the top is set and still moist, place the pan under the broiler until the top is lightly browned, 45 to 60 seconds. Slide the frittata onto a warmed dish and cut it into wedges.