Bring a large pot of salted water to a boil.
Cut the potatoes in quarters lengthwise. Using a paring knife and plenty of patience, cut each quarter into 1 or 2 torpedo- or oval-shaped pieces. Place in a large bowl of cold water while you finish the rest.
Add the potatoes to the boiling water and blanch for just under 4 minutes. (This really depends on the size of your potatoes, but be sure to not cook them for potato salad; this is just to get them slightly tender--you shouldn't be able to get a fork through them. The oven will do the rest.) Remove the potatoes from the water to a paper towel-lined plate until slightly cooled.
Preheat the oven to 375 degrees F.
Pour the potatoes into a large bowl and drizzle over enough olive oil to coat all sides. On a large baking sheet with sides, add the thyme and rosemary (whole) to make a bed of sorts. Pour out the potatoes onto the sheet and space them evenly so the air can circulate as they roast. Season the entire sheet with a pinch of salt.
Roast the potatoes until golden brown on the edges and crisp, 25 to 30 minutes.