Preheat the oven to 375ºF. Position an oven rack to the center. Line a large baking sheet with parchment paper and set it aside.
Add the Sichuan peppercorn to a spice grinder and pulse until the spice is ground (see note 3).
Transfer the ground Sichuan peppercorn, red pepper flakes, gochugaru, garlic, and 1/4 teaspoon salt to an oven-safe bowl (such as a thick glass or thick ceramic bowl, see note 4).
Heat 1/4 cup of vegetable oil in a saucepan over medium heat for about 3 to 4 minutes. The temperature of the oil should be around 325ºF.
Carefully pour the hot oil into the bowl with the peppers and garlic (see note 5). Let the oil sizzle and rest as you roast the edamame (see note 6).
In a bowl, toss the edamame with 1 1/2 tablespoons vegetable and 1/4 teaspoon salt. Spread the edamame over the lined baking sheet.
Bake the edamame for about 20 minutes. At the 15-minute mark, check to see if the edamame have browned on the bottom. If they are looking light golden, bake them for another 5 minutes. If they have barely darkened, bake them for another 8 to 10 minutes (see note 6).
Remove the edamame from the oven. Drizzle the chili oil over the roasted edamame. Make sure to incorporate the pepper and garlic sediment from the chili oil, as most of the flavor is there. Be generous! Quickly toss the edamame. Serve immediately.