Preheat oven to 325 degrees F (165 degrees C). Grease a shallow roasting pan with oil.
Cut six to eight 1-inch-thick slices vertically into the roast, stopping at least 1/2 inch from the bottom.
Heat butter and avocado oil in a large skillet over medium-high heat. Add garlic; saute until soft. Add spinach, salt, and pepper; cook and stir until spinach is wilted, about 5 minutes. Remove from heat. Stir in Parmesan cheese and coriander until evenly incorporated.
Stuff pork roast with spinach mixture, placing an equal amount between each slice. Sprinkle paprika over roast. Transfer to the prepared roasting pan.
Bake in the preheated oven until an instant-read thermometer inserted into the center reads at least 155 degrees F (68 degrees C), about 1 hour. Cover with aluminum foil and allow to rest for 10 minutes before slicing against the grain.