Preheat the oven to 375 degrees
Fry up your bacon and set aside to cool.
Take the rosemary leaves from 3 sprigs, sage leaves, and whole peppercorns and put them in a spice grinder or blender and pulse about 10 times until you have course mixture. This will be your crust.
Put your frozen spinach in a pan and get it cooking over medium high heat. Once it is mostly warmed through add in shallots and garlic. Cook 3-5 minutes.
Add in the boursin cheese and stir until completely incorporated. Add in the cherries and stir to combine.
Chop up the bacon you set aside earlier
On a sheet pan, sprinkle your herb crust mixture along with 2 tsp salt all over the pan. You will lay your pork loin on it and it will cover the loin with the crust mixture.
Take your loin and butterfly it. Cut it in half but not all the way through, you want it to still be connected a little bit.
Lay your butterflyed loin into the crust mixture and make sure it is fully covered with the mix.
Spread the spinach mixture all over the pork. Sprinkle on the the turkey bacon.
Slide 5-6 pieces of butchers twine under the pork loin. Roll the pork up and tie with the twine, with the seam side of the meat facing up.
Put on the sheet pan and into the oven with the slightly open side up so the spinach goodness doesn't melt out.
Roast 45 minutes, checking the internal temperature at 30 minutes. You want to remove it when it hits 140, then let it rest for 5-10 minutes to finish cooking.
For the sauce mix the mustard and horseradish in a small bowl
After the meat has rested, slice in 10 pieces and serve with mustard sauce.