Heat 2 tablespoons olive oil in a large skillet over medium heat. Add the bacon and cook until crisp, about 8 minutes. Add the mushrooms, 1/2 teaspoon salt, and pepper to taste; cook until the mushrooms are soft, about 4 minutes. Add the garlic and cook 1 minute. Remove from the heat and stir in the breadcrumbs and all but 2 tablespoons parsley. Let cool.
Soak 10 to 12 toothpicks in water to prevent them from burning. Rinse the pork and pat dry. Butterfly the pork: Make a 1-inch-deep incision down the length of each tenderloin; do not cut all the way through. Open the meat like a book so the tenderloins lie flat.
Cover the pork with plastic wrap; pound with the flat side of a meat mallet until about 1/2 inch thick, starting from the middle and working outward. Spread the mushroom mixture over the 2 tenderloins. Starting with a long side, tightly roll up each tenderloin. Secure the seams with the toothpicks.
Preheat a grill to medium high; brush the grates with olive oil. Brush the pork rolls with olive oil and season with salt and pepper. Grill, turning, until a thermometer inserted into the center of the pork registers 140 degrees F, 25 to 30 minutes. Transfer to a cutting board to rest, about 10 minutes.
Mix the remaining 3 tablespoons olive oil and 2 tablespoons parsley, the lemon zest, and salt and pepper to taste in a bowl. Remove the toothpicks and slice the pork rolls. Top with parsley oil.