Add oil to a large baking tray and place in oven. Preheat to 400°F.
Cut potatoes into medium/large (1.5–2 inch) chunks.
Place potatoes in a pot, cover with cold water by 1 inch, add 1 tbsp salt.
Bring to a boil, then reduce to a gentle simmer.
Cook 12–15 minutes, until fork-tender but not falling apart.
Drain immediately and let steam dry 2–3 minutes.
Shake potatoes in colander to rough up edges.
Carefully add potatoes to the hot oil and sprinkle salt over the top, then mix to ensure potatoes are fully coated.
Add garlic cut-side down.
Roast 45–60 minutes, turning every 15 minutes, until deep golden and crisp.
Remove garlic after approximately 40 minutes.
At the 60 minute mark, crank temperature up to 450°F for 10 minutes for extra crispiness.
Mix remaining sauce ingredients (crispy chilli oil, tamari, agave, rice vinegar) in a bowl.
Squeeze in the roasted garlic and mash together.
Toss hot potatoes in sauce and serve.
