Whisk marinade of worcestershire sauce, lemon juice, agave, olive oil, garlic, ginger and red pepper flakes to taste in small bowl. Rinse pork roast and place in zip top bag pouring marinade over pork. Seal bag and marinate for 15 - 30 minutes turning once to coat evenly.
Preheat oven to 450 degrees. Prep roasting pan by coating with olive oil. Place sliced onions across bottom of oiled pan. Set marinated pork roast on top of onions fat side up discarding remaining marinade and bake for 15 minutes. Reduce oven temperature to 250 degrees and continue baking for another hour to hour and a half until pork registers internal temperature of 145 or as desired.
Remove pork from oven and allow to rest for five minutes. Slice pork roast and serve.