In a small bowl, combine olive oil, minced garlic, rosemary, salt and black pepper. Set aside. Preheat oven to 450 degrees.
Using a fillet knife, double butterfly the tenderloins to flatten--make two long horizontal cuts, one on each side, which will divide the tenderloin into thirds, without cutting all the way through. Open up so that you have a large rectangle of meat. Using the heel of your hand, gently flatten the meat to 1/2" thick. Repeat with the second tenderloin.
Lightly brush insides with herb-oil mixture.
Cover each tenderloin with 4 slices of the Prosciutto, then spread 1/2 cup of the Parmesan over the ham, leaving a one-inch border.
Starting with the long side, roll up each tenderloin so that the stuffing is in a spiral pattern. Tie the roasts with cooking twine every 2 inches. Lightly brush roasts with remaining herb-oil mixture.
Heat a large skillet with oil. Add the roasts and cook, turning to coat the outsides until browned.
Transfer the tenderloins to a baking sheet lined with foil and place in the preheated oven. Cook for 15-20 minutes until internal temperature reaches 145 degrees. Remove from heat and tent with foil. Let rest for 5 minutes.
To serve, remove the string and cut into 1" slices. This will serve 10-12.