For the chili oil: Bring the chilies and oil to a simmer in a small saucepan; remove from the heat and let the peppers steep in the oil for at least an hour or until the dough has risen and you're ready to make the pizzas. This can be done way in advance.
For the dough: In a small bowl, add 1/2 cup warm water (if the water is too hot the yeast will die and if the water is too cold the yeast will not activate). Add the dry yeast and sugar, stir to combine and let sit for 15 minutes. The top of the water will bubble and it will smell very yeasty; this is what you want.
In a large mixing bowl, combine the flour and salt. Make a well in the center of the flour and add the olive oil and the yeast/water mixture. Using a fork, gradually stir the flour into the yeast/water mix. Once most of the flour has combined, turn the dough out to a smooth, clean work surface dusted with flour and use your hands to knead the dough to a smooth consistency.
Lightly coat the mixing bowl with oil, return the dough to the bowl, cover with plastic wrap and set in a warm place until the dough has doubled in size, at least 1 hour.
For the pizza topping: Coat a large saute pan with oil, add the sausage and bring to medium heat. Cook the sausage until brown, 10 to 15 minutes. Remove with a slotted spoon and reserve.
While the sausage cooks, mix together in a medium bowl the ricotta, Parmigiano-Reggiano and oregano.
Preheat the oven to 425 degrees F and preheat a grill.
When the dough is ready, portion it into six golf-ball-size pieces. (If you're not using the dough right away, wrap each ball individually in plastic and refrigerate until ready to use.) Dust a work surface with flour and roll each piece of dough into a rectangle (or whatever shape you like; I like irregular shapes).
Brush the grill with oil and arrange each piece of dough on the grill; you might need to work in batches here. Grill until the dough is stiff and crisp and has lovely grill marks on it, then flip and repeat on the second side, moving occasionally so the bottom doesn't burn.
Put the pizzas on baking sheets, smear each with some of the ricotta mixture, top with sausage and put as many pizzas as will comfortably fit in the oven; bake until the cheese has melted, 3 to 4 minutes. Again, you may have to work in batches. Remove the pizzas from the oven, top with arugula and drizzle with the deliciously spicy chili oil!
Adapted from "Cook Like a Rock Star" by Anne Burrell. Copyright Clarkson Potter 2011. Provided courtesy of Anne Burrell. All rights reserved.