Bring the oil to medium-high heat in a medium, heavy-bottomed pot with a tightly fitting lid. Add the prosciutto and crisp until it is lightly golden and the fat renders, about 1 minute. Add the carrots, peppers and onions and cook until softened, about 3 minutes. Stir in the orzo and rice. Toast until the grains are all evenly coated with oil, about 3 minutes.
Pour the broth and lemon juice into the same pot. Bring to a boil. Add the garbanzos and bay leaf and stir to combine. Cover, reduce the heat to medium-low and simmer until the orzo and rice are tender. Remove from the heat once the liquid is fully absorbed, 12 to 15 minutes.
Let the pilaf stand, covered, for 5 full minutes. Fluff with two forks, remove the bay leaf and season with salt and pepper. Stir in the scallions and serve garnished with the basil and mint leaves.