Place an unwrapped prime rib on a tray. Generously salt all over and refrigerate overnight to air-dry the outside of the prime rib.
Bring the prime rib to room temperature before roasting. It usually takes about 2 hours out on the counter.
Mix the cumin, black pepper and garlic powder and evenly spread all over the meat.
If roasting garlic, slice the top off, drizzle some olive oil and wrap in a foil. (Here's my detailed roasted garlic recipe.)
Preheat the oven to 200°F (95°C).
Place the prime rib on a roasting pan bone side down (fat side up). (Since I wrote this post, I bought this roasting pan, and highly recommend it.) Roast the meat in the oven until the center of the roast reads 120°F (50°C) on a meat thermometer for medium-rare, or 130°F (55°C) for medium doneness, about 3.5-4 hours. (This Thermapen Mk4 meat thermometer is my favorite! Super quick and reliable! <- affiliate link)
Remove the prime rib from the oven, cover with a foil and rest for about 30 minutes.
Increase the oven temperature to 500°F (260°C).
10 minutes before serving, pop the prime rib into the oven, uncovered, and cook it until it’s nice and brown, and crisp on the outside, about 6-10 minutes. If desired, roast the cherry tomatoes and asparagus together. Serve immediately.