Preheat oven to 400°F.
For the sauce, heat a heavy Dutch oven or deep skillet over medium-high heat and add olive oil, 2 turns of the pan. Add fennel, peppers, onions, garlic and some salt, and cook, partially covered, until soft, about 10 minutes, stirring occasionally. Hand-crush tomatoes and add them and their juices to the pan. Simmer over medium-low heat for 20 minutes.
Meanwhile, bring a few inches of water to a boil in a deep skillet. Salt the water, add broccoli rabe and cook 3 minutes; drain. Arrange broccoli rabe on a baking sheet lined with foil or parchment, dress with EVOO, salt, crushed garlic and chilies. Roast the broccoli rabe until crispy at edges and tender, 15-18 minutes.
For the pesto, process the herbs, walnuts, garlic and cheese into a fine chop. Stream in oil with the machine running to form a pesto sauce. Season with salt and pepper to taste.
Place a rack in the upper third of the oven. Split hoagie rolls lengthwise and spread both sides lightly with pesto, reserving the extra. Toast rolls in oven for 3-5 minutes, remove and switch oven to broil.
Fill the toasted rolls with some roasted broccoli rabe, top with the fennel, peppers and onions and some mozzarella or provolone. Melt cheese under broiler, dot with extra pesto sauce and serve.