Preheat the oven to 350.
Mix the mustard and next 6 ingredients together in a bowl and set aside.
Cut the pork loin so it lays flat: starting about 1/2 inch from the edge of the longest side, make a slit that goes within 1/2 inch of the bottom of the loin without cutting through it. Open the meat at the cut and repeat the cut without going through. You should end up with a fairly flat, rectangular shape when you are done.
Cover with plastic wrap and pound to an even thickness of just under 1/2 inch if you can. (Mine was thicker.)
Spread all but 1 tablespoon of the mustard mixture inside the loin and roll up like a jellyroll.
Place the loin seam side down in a baking dish, and coat with the olive oil. Bake 30 minutes.
Add the remaining tablespoon of mustard mix to the top of the loin and continue baking until the center registers 160–about 10 minutes more. Let stand 10 minutes before slicing.