A popular misconception is that to make a good roast you gotta put a rainbow of spice, cover it in a mountain of pineapple, smear with sugar ... Don't get me wrong, you can get some really good ones that way, but just like with steak - less is more.
Spices here are salt and pepper. Garlic, of course, add the flavor, but it;s used to also seal the skin on the meat with garlic glaze.
There's is a spoon of oil used here, yes, but some oil is good. You won't do any good excluding completely ingredients from your ration. Think of it as a grease for the wheels in the machine that your body is. A lot of it will clog it up, just just a little smear will keep the wheels turning. Same goes for salt, by excluding salt you open yourself to often bloating whenever you inject salt unwillingly.
1 tbsp salt
1 tbsp letter
3 tbsp garlic, chopped small
1 tbsp olive oil
1. Preheat oven to 450 F. Meanwhile, wash the roast and dry it with a paper towel so water doesn't repel the rub. The dryer the better, it will crisp faster this fay in the oven.
2. Blend salt, pepper, garlic and oil together into paste (chopping small works, too)
3. Rub garlic paste on the roast and bake it for 30 min to seal paste on the surface of the roast.
4. Lower temperature of the oven to 350 and bake for 3-5 hours, depending on the size of the roast. Check the meet with thermometer and make sure that it's cooked till 185 F inside.
5. Take it out of the oven and let it rest at least for 15 min before handling.
There is NO way of knowing if roast is cooked by the look of the meat, it's a big chunk and it gets color in first 30 min, after which is slowly cooks without drying out and loosing its juices.
Also, let your mat to sit on he table a bit before baking it so the inside of the meat is not cold from the fridge. This way it will cook evenly, otherwise it will be thawing instead of cooking.