Preheat oven to 475°F. Line a baking sheet with parchment paper.
Toss green beans with oil, and then sprinkle with salt and pepper. (You can do this in a bowl before spreading the beans on the baking sheet, or you can do it directly on the baking sheet. Either way, just be sure that all the beans are evenly coated in oil, and that the salt and pepper are evenly distributed.)
Arrange green beans in a single layer on the parchment-lined baking sheet. Don't over-crowd them (use a second baking sheet if needed), or they won't roast properly.
Roast beans for about 10 minutes (until some browned, blistered spots are beginning to form), and then stir and flip them over, again spreading them evenly out across the baking sheet.
Return beans to the oven and continue roasting for about another 10 minutes (optionally stirring one more time halfway through), until the green beans are roasted and blistered to your liking.
Trimming green beans: I prefer to leave the "tails" of the green beans on, but that's entirely optional, and if you prefer, you can trim away the tails as you cut off the stem ends.
Doneness: For this "blistered" recipe, I do truly like for there to be deeply roasted spots on the green beans. However, if you would like yours to be slightly less roasted and blistered, you can simply reduce the total roasting time. Instead of 10 minutes before stirring, followed by another 10 (20 minutes total), you could try just 8-9 minutes before and after stirring (16-18 minutes total).
Make-ahead tips: You can rinse and stem the green beans a few hours earlier or the day before. Make sure they are thoroughly dry, and then store them, wrapped, in the refrigerator. You can also go one step further and spread the rinsed, trimmed, and dried beans on the parchment-lined baking sheet, wrapping the whole sheet in plastic, and refrigerating until you're ready to continue with the recipe.
To make Blistered Green Beans with Red Potatoes: Toss 1 pound of red potatoes (cut into about 1-inch pieces) with an additional 1 1/2 teaspoons of extra virgin olive oil, 3/4 teaspoon kosher salt and 1/4 teaspoon black pepper. Spread them evenly on an additional parchment-lined baking sheet (separate from the green beans) and proceed with cooking instructions above. However, once the green beans are done cooking and have been removed from oven, the potatoes should be left in the oven for approximately 5 additional minutes. (As a side note, because this recipe is labeled as paleo: many very strict paleo regimens exclude potatoes, so while the Blistered Green Beans are paleo, combining the beans with potatoes may or may not fit your paleo regimen.)