When October evenings turn crisp and the first frost silences the garden, my kitchen transforms into a sanctuary of warmth and scent. One bite of these crispy roasted potatoes and sweet potatoes with herbs instantly transports me back to my grandmother’s farmhouse table, where we’d huddle around a chipped enamel platter piled high with sunset-orange hunks of sweet potato nestled against mahogany-edged russet coins. The windows fogged, the old radio crackled with jazz, and everything smelled of rosemary, garlic, and possibility.

I created this recipe for busy weeknights when you crave that same nostalgic comfort but need it to land on the table without fuss. It’s elegant enough for a Sunday roast chicken, yet unfussy enough to snuggle beside a quick omelet on a Tuesday. The dual potatoes—earthy russets and honey-sweet sweet potatoes—mean every forkful toggles between savory and subtly sugary, while a bold herb oil lacquers the edges into shattering crisps. If you’ve been disappointed by soggy tray bakes in the past, prepare to convert: these spuds stay fluffy inside and audibly crunchy outside, even after a gentle reheat tomorrow for lunch.

Why This Recipe Works

Two-Stage Roast: A hot preheat plus a single flip guarantees glass-crisp edges without over-browning.
Starch Swap: A quick par-boil with baking soda roughs up surfaces for maximum crunch.
Herb-Infused Oil: Warm olive oil blooms dried herbs and garlic so every crevice carries flavor.
Dual-Temp Taters: Russets and sweet potatoes roast together by cutting the denser russets slightly smaller.
Sheet-Pan Zen: Everything cooks on one pan, meaning fewer dishes and more caramelization.
Make-Ahead Magic: Cool, refrigerate, then re-toss in a skillet for five minutes to restore snap.

Ingredients You'll Need

Look for medium-starch russets (often sold as “baking potatoes”) with tight, unblemished skins; they fluff beautifully while turning glass-like at the edges. For sweet potatoes, the copper-skinned Garnet or deep-orange Beauregard varieties roast sweetest—avoid the pale, dry-fleshed Asian varieties here unless you enjoy a more starchy result. Buy organic if you can; you’ll leave the nutrient-rich skins on.

Extra-virgin olive oil is my go-to because its fruity bitterness balances the tubers’ natural sugars. If you only have light olive oil, swirl in a teaspoon of good balsamic at the end for complexity. Dried herbs are bloomed in warm oil; if you prefer fresh, double the quantity and add them only after roasting so they stay vivid. Smoked paprika quietly amplifies the sweet potatoes’ caramel notes, but regular paprika works too. Finally, a whisper of cornstarch (our secret weapon!) wicks away surface moisture for audible crunch—don’t skip it.

Need substitutions? Avocado oil is a neutral high-heat stand-in. Yukon Golds can replace russets but will taste creamier rather than fluffy. Vegan? The recipe already is. Low-sodium? Swap the kosher salt for half as much fine sea salt and season to taste at the table.

How to Make Crispy Roasted Potatoes and Sweet Potatoes with Herbs for Warm Dinners

Heat the sheet pan

Place a rimmed 13×18-inch sheet pan on the lowest rack of your oven and preheat to 425 °F (220 °C). A screaming-hot surface jump-starts crisping while the oven climbs to temperature.

Par-boil with baking soda

While the oven heats, bring 3 quarts of water to a boil in a large pot. Add ½ teaspoon baking soda and 2 tablespoons kosher salt. The alkaline water breaks down pectin, creating a fuzzy starch layer that dehydrates into crunch.

Prep the potatoes

Scrub and dry 2 pounds russet potatoes; peel 2 pounds sweet potatoes if you prefer (I leave the skins on for fiber). Dice russets into ¾-inch chunks and sweet potatoes into 1-inch pieces—the slight size difference equalizes roasting times.

Boil and rough-up

Add russets to the boiling water first; cook 5 minutes. Stir in sweet potatoes and cook 4 minutes more. Drain aggressively: shake the colander so edges fray. Let steam-dry 2 minutes—evaporation is your friend.

Seasoning paste

In a small saucepan, warm ½ cup olive oil with 2 teaspoons dried rosemary, 1 teaspoon dried thyme, 1 teaspoon smoked paprika, ½ teaspoon freshly cracked black pepper, and 4 smashed garlic cloves until fragrant (do not fry). Off heat, whisk in 1 tablespoon cornstarch.

Toss vigorously

Transfer potatoes to a large bowl. Pour the herb oil over, sprinkle with 1½ teaspoons kosher salt, and fold with a rubber spatula for 30 seconds. The abrasion helps build a pastelike coating that bakes into a crunchy shell.

Roast hot and fast

Carefully slide the potatoes onto the preheated pan in a single layer; listen for the sizzle. Roast 25 minutes. Flip each piece with a thin metal spatula, rotate the pan, and roast 15–20 minutes more until deeply golden.

Finish fresh

Transfer to a serving bowl. Shower with chopped parsley, lemon zest, and flaky sea salt. Serve immediately for maximum crunch, or let cool completely before storing (see storage section).

Expert Tips

Use a dark pan

Darker metal absorbs heat, promoting browning. If yours is light, add 3 extra minutes to the second roast.

Don’t crowd

Overcrowding steams. If doubling, split between two pans on separate racks and swap halfway.

Dry equals crunchy

If you rinse potatoes, spin them in a salad spinner or towel-dry zealously before oiling.

Flip once

Multiple stirs cool the pan. A single confident flip keeps edges intact and heat steady.

Season post-roast

A final pinch of flaky salt adds pops of salinity without drawing out moisture during roasting.

Re-crisp like a pro

Reheat in a dry cast-iron skillet over medium heat, shaking occasionally, for five minutes.

Variations to Try

Spicy Harissa: Replace smoked paprika with 1½ teaspoons harissa powder and a pinch of cayenne. Finish with cilantro and lime.
Maple-Sage: Swap rosemary for crumbled dried sage and drizzle 2 tablespoons maple syrup during the final 10 minutes for candied edges.
Lemony Greek: Use dried oregano and a pinch of nutmeg. Toss finished potatoes with chopped dill, lemon juice, and crumbled feta.
Parmesan Truffle: Add ¼ cup grated Parm to the cornstarch step. After roasting, mist with truffle oil and shower with more Parm.

Storage Tips

Refrigerator: Cool completely, then refrigerate in a shallow airtight container up to 5 days. To preserve texture, place a paper towel on top to absorb condensation.

Freezer: Spread cooled potatoes on a parchment-lined tray; freeze until solid, then transfer to a zip bag for up to 2 months. Reheat directly from frozen in a 450 °F oven for 12–15 minutes.

Make-ahead: Par-boil and oil-toss up to 24 hours ahead; keep chilled in a bowl covered with plastic wrap. Spread on the hot sheet pan and roast as directed—add 3 extra minutes to the first roast.

Frequently Asked Questions

Absolutely. Halve them and reduce the par-boil to 3 minutes total. Roast 20 minutes, flip, then 10–12 more.

Sweet potatoes contain more moisture and sugar; the cornstarch and hot pan are crucial. Be sure they’re dry, well-coated, and not crowded.

You can, but crunch will suffer. Swap for arrowroot or potato starch if you avoid corn.

Pile into a heat-proof serving dish, tent loosely with foil, and hold in a 200 °F oven up to 30 minutes. Leave a small gap so steam escapes.

Yes. Cornstarch is naturally gluten-free; be sure yours is certified if you’re highly sensitive.

Microwaving doesn’t rough up starch as effectively, so you’ll get less crunch. In a pinch, microwave covered with ¼ cup water 6 minutes, then drain well.