In a large pot bring water to a boil on high heat adding a generous amount of salt. Add the pasta, stirring occasionally so as not to stick and cook according to suggested time on the box of the pasta less 1 ½ minutes. Reserve a cup of cooking water.
Place a large and deep pan over medium heat and add the guanciale. Cook for about 5’ until golden and crispy. Remove from the heat to a plate lined with kitchen paper and keep aside.
In the same pan add the butter and allow to melt. Add the onions, carrots and celery and cook for about 5’ and until softened. Add the garlic along with the rosemary and sage and cook for 1’ and until fragrant. Pour the wine and allow to evaporate.
Add the tomatoes, cover with the lid askew and simmer for about 50’ and until the sauce has thickened, making sure that you stir every now and then as well as breaking the tomatoes with a wooden spoon.
Remove the rosemary sprigs and place the sauce in the bowl of a food processor with the metal blade attached. Pulse few times until a rough sauce has been created.
Return the sauce to the pan over low heat and add 3/4 of the guanciale along with the chili flakes and season with the salt and pepper.
Strain the pasta and return to the pan with the sauce along with some of the reserved water and cook for another a minute.
Serve and add some pecorino cheese along with the remaining guanciale and the parsley.