In a large pot, bring 4 quarts water to a boil.
In a blender, puree the tomatoes with juices and gochujang until smooth, 30 to 60 seconds; set aside.
While the water heats, in a 12-inch skillet, combine the oil, pancetta, garlic, bay, tomato paste, rosemary and ½ teaspoon pepper.
Cook over medium, stirring often, until the pancetta has rendered some of its fat and the tomato paste darkens and begins to stick to the pan, 6 to 8 minutes.
Add the pureed tomato mixture and bring to a simmer, scraping up any browned bits.
Simmer, uncovered and stirring often, until very thick and the fat separates, about 10 minutes.
Meanwhile, when the water reaches a boil, add 1 tablespoon salt and the pasta; cook, stirring occasionally, until just shy of al dente.
Reserve about 1½ cups of the cooking water, then drain the pasta and return it to the pot.
Scrape the sauce into the pot with the pasta and add ¾ cup of the reserved cooking water.
Cook over medium, stirring and tossing often, until the sauce clings and the pasta is al dente, 2 to 4 minutes; add more reserved pasta water as needed to loosen the noodles if the mixture is very dry and sticky.
Off heat, remove and discard the bay and rosemary.
Taste and season with salt and pepper, then stir in the basil.
Serve topped with dollops of ricotta.
