Wraps: Preheat oven to 350 F. Slice the tops of the peppers and cut in half, taking out the core and seeds. Cut the sweet onion into slices. Toss the peppers and onions with olive oil, salt and pepper; roast in the oven until the vegetables start to caramelize (approx. 35-45 minutes.) Remove from the oven.
While the peppers and onions are cooling, wash the Napa cabbage. Use the smaller leaves to make small wraps; you will have plenty of leftover cabbage to use for another recipe. When peppers are cool enough to handle, slice into thin strips.
Crème Fraiche Adobo Sauce: With a mini food processor, blend together the crème fraiche, one tablespoon of the adobo sauce, and one chipotle pepper from the can. Put the mixture into a squeeze bottle.
Lay out the cabbage leaves on a platter. Assemble each wrap to your liking: top with the mixture of peppers and onions, shredded roasted chicken, queso fresco, and cilantro. Finish with a drizzle of the spicy crème fraiche adobo sauce.