Snap bottoms off of asparagus, use a vegetable peeler to peel spears and steam them to a point where they are not totally wilted. Refrigerate until needed.
Lay out pieces of prosciutto and spread about one tablespoon of Boursin cheese onto each slice. Mean Chef has a recipe if you find it hard to locate in your local market -- Boursin Cheese - Make your own Recipe #65204.
Put chilled asparagus spears on kitchen towels to absorb any moisture. Place one or two asparagus spears in each slice of prosciutto and roll. Refrigerate if not serving immediately.