Place a rack in the center of the oven. Preheat the oven to 425 degrees F.
In a large heavy saucepan or braising pan, cook the bacon over medium-high heat until crisp, 8 to 10 minutes. Using a slotted spoon, remove the bacon and drain on paper towels.
Add the onions, salt and pepper. Reduce the heat to medium-low and cook until tender, about 5 minutes. Add the rice and stir for 2 minutes. Add 3 cups broth and the lemon juice. Increase the heat and bring the mixture to a boil, stirring occasionally. Cover with a tight lid and bake in the oven for 20 to 25 minutes.
Remove the pan from the oven and return it to the stove over medium-low heat. Remove the lid and stir in the chicken, kale, roasted vegetables and 1/4 cup chicken broth. Stir until the kale is wilted, about 5 minutes, adding extra broth, as needed, until the risotto is creamy. Stir in the cooked bacon and cheese. Ladle into bowls and serve.