There’s something about a slow-roasted rib roast that brings people to the kitchen before dinner’s even ready. It’s that mix of garlic, fat, and crispy edges floating through the house that makes everyone hang around, checking the oven like it’s a movie premiere. Now, pair that with a bright, herby chimichurri sauce that packs flavor without carbs and you’ve got a keto meal that feels like cheating, but isn’t.

This is the kind of dish that doesn’t need a side story or a fancy pitch. You want a proper roast, juicy and rich, with a bold sauce that doesn’t taste like it’s missing anything. That’s what this Keto Chimichurri Rib Roast is. No drama. Just flavor.

Let’s get into it.

What Is a Rib Roast?

A rib roast comes from the primal rib section of beef — the same area you’d get ribeye steaks from. It’s known for being fatty, tender, and loaded with flavor. You can get it bone-in (called a standing rib roast) or boneless. For this recipe, bone-in gives better flavor and presentation, but boneless works too if that’s what you’ve got.

It’s sometimes called a prime rib — but “prime” refers more to the USDA grade. So technically, any rib roast can be called “prime rib” if it’s from that cut, even if the grade is Choice or Select.

What matters here is fat marbling and patience.

Why This Recipe Works So Well for Keto

Fat is your friend on keto. This roast has plenty. The outside crisps up like bacon, and the inside stays tender and pink. It’s high in fat, moderate in protein, and has zero carbs if you don’t mess around with starchy sides or sugar-rubbed seasonings.

The chimichurri? That’s the magic. Traditional chimichurri already leans keto, but some recipes sneak in breadcrumbs or sweeteners. We’re not doing any of that. Ours is clean: herbs, garlic, vinegar, oil, no sugar — nothing weird.

Ingredients You’ll Need for this Recipe

Let’s break it down:

For the Rib Roast (Serves 6-8):

1 bone-in rib roast (4 to 6 pounds)
2 tbsp kosher salt
1 tbsp freshly ground black pepper
1 tbsp garlic powder
2 tsp dried thyme
2 tsp dried rosemary
2 tbsp olive oil or melted beef tallow

For the Keto Chimichurri:

1 cup fresh flat-leaf parsley (firmly packed)
1/4 cup fresh oregano (or 1 tbsp dried)
4 garlic cloves
2 tbsp red wine vinegar
1/2 cup olive oil
1/2 tsp crushed red pepper flakes (optional)
Salt to taste
Black pepper to taste
Juice of 1/2 lemon (optional but adds brightness)

Kitchen Tools You’ll Need

Roasting pan with rack
Meat thermometer (seriously, don’t skip this)
Food processor or blender (for chimichurri)
Cutting board and carving knife
Aluminum foil

Step-by-Step: How to Make Keto Chimichurri Rib Roast

Let’s walk through it slow and proper — no skipping, no rushing.

1) Prep the Meat (Don’t Overthink It)

Take your rib roast out of the fridge at least 1 to 2 hours before cooking. Letting it come closer to room temp helps it cook evenly. If you throw a cold roast into a hot oven, the outer layer burns before the inside catches up.

Pat it dry with paper towels. Water is the enemy of a good crust.

Rub the roast all over with olive oil or beef tallow. This helps the seasoning stick and adds extra crisp.

Mix your salt, pepper, garlic powder, thyme, and rosemary in a bowl. Rub that mix all over the roast, pressing it into the fat and meat.

Let it sit uncovered while the oven preheats.

2) Low and Slow Is the Trick

Preheat your oven to 250°F (120°C). Low heat lets the roast cook evenly, end to end, so you don’t get a gray ring around a pink center. You want that blush from edge to edge.

Place the roast bone-side down on a rack in a roasting pan. If you don’t have a rack, make a “raft” of cut onions or halved garlic bulbs to hold it up. It keeps the meat from sitting in its own drippings.

Insert a meat thermometer into the thickest part, avoiding bone.

Pop it in the oven and roast until the internal temp hits 120°F (for rare), 125°F (medium rare), or 130°F (medium). This usually takes about 3 to 4 hours depending on the size of your roast.

Don’t keep opening the oven. Let the thermometer do its thing.

3) Rest. Then Blast.

When the roast hits your desired temp, pull it out and let it rest for 30–40 minutes. Tent it loosely with foil, don’t wrap it up tight — you don’t want it to steam and soften the crust.

During this rest, crank your oven up to 500°F (260°C).

After it’s rested, pop the roast back into the hot oven for 10 minutes. This gives you that golden, crunchy crust people fight over.

Pull it out and rest again, just 10 minutes this time, while you finish the chimichurri.

Make the Chimichurri (Takes 5 Minutes, No Cooking)

While your roast is doing its thing, whip up the sauce.

Add parsley, oregano, garlic, vinegar, salt, pepper, and red pepper flakes to a food processor or blender. Pulse a few times until it’s chopped but not pureed.

With the motor running, drizzle in olive oil slowly. You want a chunky texture, not a smoothie. Taste and adjust salt, pepper, or vinegar. If it’s a little sharp, add a squeeze of lemon to mellow it.

Let it sit at room temp — chimichurri gets better as it sits.

Slice and Serve

Carve the rib roast by cutting between the bones. If it’s boneless, just slice it like a loaf. Each slice should be juicy with a deep pink center, a dark crust, and drippings that smell like holiday mornings.

Serve each portion with a spoonful of chimichurri right on top or on the side.

What to Serve With It (Still Keto)

Here are some ideas to make it a full meal without knocking yourself out of ketosis:

Roasted cauliflower mash – buttery, smooth, and so close to mashed potatoes you’ll forget they’re not
Garlic green beans – sautéed in bacon fat, no one’s complaining
Keto creamed spinach – heavy cream, nutmeg, a little garlic
Grilled zucchini or asparagus – simple and fast
Buttered mushrooms – cook them in the pan drippings after your roast is done

Or just serve it solo. It’s that good.

Leftover Ideas That Don’t Feel Like Leftovers

Let’s be honest — you’re gonna have some roast left. Don’t let it go boring.

Keto steak and eggs the next morning — fry the meat in butter until crisp
Low-carb beef tacos — wrap in lettuce, top with chimichurri, avocado, maybe a little cheese
Shaved beef salad — over arugula with olive oil, lemon juice, and sliced almonds
Keto Philly cheesesteak bowl — meat, sautéed peppers, onions, cheese on top

It reheats best in a skillet, not a microwave. Or eat it cold from the fridge — no shame in that.

Tips That Make a Big Difference

Don’t skip the thermometer.

Guessing doneness doesn’t work here. Overcooking this cut is a crime. If you don’t have a meat thermometer, get one. Cheap ones work fine.

Fat cap side up.

This lets the fat melt into the meat as it cooks. More flavor, more moisture.

Rest twice.

Once before searing (the big rest) and once after (short rest). This keeps juices inside the meat instead of all over your cutting board.

Don’t over-blend the chimichurri.

It’s not pesto. You want texture — leafy, oily, bright.

Make extra sauce.

It keeps in the fridge for a week and goes on everything: grilled chicken, eggs, roasted veggies, steak, even shrimp.

What Makes This Worth It

You don’t need fancy tools. You don’t need hard-to-find ingredients. Just solid meat, fresh herbs, and a little patience. This roast looks impressive, tastes rich, and doesn’t mess with your macros.

Keto or not, people will ask for seconds.

I’ve made this roast on birthdays, around the holidays, and even on random Sundays when I needed a dinner that felt like a win. It always hits. The crispy crust, the juicy center, that green sauce soaking into each bite — it’s worth every minute in the kitchen.

Conclusion

This isn’t just a recipe. It’s a keeper. It feeds a crowd, makes leftovers you’ll actually eat, and doesn’t kick you out of ketosis. What more can you ask for?

If you’re scrolling through Pinterest looking for that one recipe that’s going to actually be worth cooking, this is it. Print it, save it, screenshot it — and make it your own.

You’ll come back to it. Again and again.