Prepare the Salad: Place the salad mix in 1 of the plastic bags and keep refrigerated. Combine the remaining ingredients in the second plastic bag and shake to mix.
Make the Pinwheel: Layer the mozzarella with the prosciutto, and roll it up tightly-squeeze hard to keep it rolled up. (If using 2 square slices cheese, lay them end to end, slightly overlapped, to create 1 long slice.) Slice the roll into 4 equal-sized pinwheels and place them in the bottom of the bag with the vegetables and refrigerate.
To serve, arrange the lettuce in a bowl and cover the vegetables and pinwheels.