Preheat the oven to 375 degrees F. Line a baking sheet with parchment paper. Bring a large pot of water to the boil. Add the asparagus and cook 1 minute. Drain well, cool in ice-cold water and drain well again. Lay a half piece of prosciutto on a work surface. Set 3 to 5 asparagus spears at one end of the prosciutto. Tightly roll the prosciutto around the asparagus and place on the baking sheet. Repeat
with the remaining asparagus and prosciutto. Sprinkle the bundles with the oil, vinegar and pepper. Roast for 15 to 20 minutes, and then serve.
Note: Asparagus can vary in thickness. If thick, you only need to roll 3 spears in each bundle. If thin, you'll need 4 to 5 spears in each.