Preheat oven to 500 degrees (yes, 500).
Rinse, and pat dry the pork roast. Set aside on a clean plate.
In a food processor or blender, combine onion, garlic and parsley. After all is minced and mixed well, slowly add (while pulsing) olive oil until a nice thick paste has formed. This should be enough paste to completely cover a 3 lb. roast. If you use a bigger roast, then increase the amounts of the ingredients for the paste accordingly. If your paste isn't, well, pasty enough, add more olive oil until it is. Maybe your onion or garlics were bigger than mine.
Rub a 1/4 inch thick layer of the paste on to what you have decided to be the bottom of your roast. When completely covered, carefully put bottom side down onto a wire rack that is set onto a broiler pan. If you don't mind your roast sitting in a little fat and possibly getting brown on bottom, you could omit the use of the wire rack.
Now, apply the rest of the paste to the top and sides of the roast. When completely covered, sprinkle Kosher salt all over top and then sprinkly as evenly as possible the juice of the lemon on top of all.
Now, with rack in the second lowest position, put roast uncovered in the 500 degree oven for 17 minutes. Then, LOWER TEMP of oven to 325 degrees and cook for approximately one more hour OR until temperature taken from probe reads 155 degrees. When done, take roast out and allow to rest for 10-15 minutes loosely covered with foil. Resist the urge to cut into it at least for the first 5 minutes to allow the juices to redistribute. You wont be sorry, because this is one juicy hunk o' meat!
While the roast is cooking at 500 degrees, coat the baby carrots, potatoes and onion with the Kosher salt and olive oil and cook them in the oven with the roast AFTER lowering the temp to 325. When you remove the roast from the oven, crank the heat on the veggies back up to 415 degrees and by the time the juices in the roast have redistributed, your veggies should be crisp-tender and ready to be enjoyed with the roast. Perfecto! I love multi-tasking.
By the way, all ovens are calibrated differently. My cooking times are based, of course, upon my oven.so be sure and check the temp of your roast with an internal thermometer inserted into a fleshy part of the meat (avoid taking temp near bone where temperatures will register higher). If covered properly with foil while standing, the pork roast will raise in temperature to the proper and recommended safe temp for pork. I did have some burned looking juice on the bottom of the pan, but the roast was excellent.