Place the oven rack on the middle position and preheat the oven to 450°F. Toss cut cauliflower, olive oil and salt on a sheet pan and roast until tender and golden brown, 20-25 minutes.
Meanwhile, place the prosciutto in a single layer on another sheet pan and roast in the same oven for 5 minutes. Let the cauliflower and prosciutto come to room temperature. Once the prosciutto is cooled, rough chop it into bite-sized pieces and set aside.
In a small bowl, combine all the vinaigrette ingredients and whisk OR place all the vinaigrette ingredients into a jar with lid and shake until combined. Set aside.
In a large bowl, gently toss together arugula, cauliflower, prosciutto and Parmesan (keep some of the prosciutto and Parmesan aside for garnish) with the vinaigrette. Garnish with remainder of the prosciutto and Parmesan. *Add additional fresh cracked paper if desired.