In a large pot of water, cook the penne according to package directions. Before draining, reserve 1/2 cup of the cooking water. Drain and set aside.
In a large, heavy skillet, sauté the prosciutto or pancetta in a drizzle of olive oil over medium-high heat until crisp. Add the tomatoes and cook until the skins are slightly blistered. Add the peas (they can go in straight from the freezer, even) and cook for a few minutes. Return the pasta to the pan, season with salt and pepper and add the cooking water, tossing to combine everything and create a bit of sauce. Add the Romano, too.
Serve immediately, passing extra grated cheese at the table.