Preheat the oven to 425°F. Line a large baking sheet with parchment paper and set aside. If your baking sheet is well-seasoned, you can skip the parchment lining.
Make the dip: Cut the top ½ inch off of the garlic head. Tear a piece of foil (enough to wrap around the garlic) and place the garlic head in the middle. Drizzle oil on top, letting it seep into the garlic cavities. Wrap the garlic up and place it in the oven. Roast the garlic until squidgy and golden inside, about 45 minutes. Set aside to cool.
Place the yogurt into a small bowl. Squeeze the cooled roasted garlic into the bowl. Add the lemon juice, tahini, parsley, mint, salt, and pepper to the yogurt mixture. Mash and stir it all together with a fork until combined. Cover the bowl and set aside in the refrigerator.
Make the fries: Cut the sweet potatoes into 3-inch long and ½ -inch thick fries. Place the cut sweet potatoes into a large bowl and cover them with cold water. Let them sit for at least an hour or up to overnight in the refrigerator.
Drain the sweet potatoes and lay them on a clean kitchen towel. Place another clean kitchen towel on top and loosely roll them all up. Massage the little towel sweet potato roll-up for a bit so that the fries are as dry as possible.
In another large bowl, toss the cut sweet potatoes with the arrowroot powder and SALT-FREE seasonings of your choice (salt is happening later). The cut sweet potatoes should have a light, powdery coating of arrowroot.
Spray the parchment on your baking sheet evenly with the oil spray. Arrange the sweet potatoes in rows on the baking sheet. Spray the tops of the sweet potatoes with the oil spray before sliding them into the oven.
Bake the sweet potato fries for 25 minutes or very lightly browned in spots and the arrowroot is forming a light “webbing” on the undersides of the fries. Remove the fries from the oven and carefully flip them all over. Slide the sweet potato fries back into the oven and bake for another 25 minutes.
At the end of the 25 minutes, the sweet potato fries should have some strong brown spots and crisp exteriors. If they still look like they need crisping, carefully flip them one more time and bake until they’ve reached your desired doneness.
Quickly transfer the fries to a large bowl and toss them with a fat pinch of sea salt. Warning: when they’re piping hot, they won’t FEEL completely crispy yet. Place the hot fries on your serving plate in a single layer along with your roasted garlic tahini yogurt dip. After they sit for a few seconds, they will start to get that super crispy quality.