Preheat oven to 350 degrees F.Lay fennel and cauliflower flat on sheet pan and roast for 30 minutes, turning occasionally, until tender. Remove from oven and set aside.Add olive oil to a large pot over medium heat. Add the onions and saute for five minutes, until translucent. Add the garlic and saute for 1 - 2 minutes, until fragrant. Add the roasted fennel and cauliflower, vegetable broth, and garbanzo beans. Bring to a boil, then simmer for 10 - 15 minutes.Add one tablespoon fresh dill and blend the soup by using an immersion blender or transferring it to a regular blender. (If using a regular blender, be very careful as the steam can sometimes cause the lid to blow off. I recommend blending small batches while holding the lid down with a pot holder or towel in hand.)Before serving, add sea salt and black pepper to taste. Garnish bowls with remaining fresh dill, lemon zest, a drizzle of olive oil, and serve with lemon wedges.