Seemingly every supermarket and convenience store sells roasted peanuts, but the flavor of freshly roasted peanuts, still warm from the oven, is much more robust. The most critical aspect of preparing roasted peanuts at home is determining when they are done roasting, because their visual appearance does not change as noticeably as most other foods while they cook. When in doubt, remove a peanut from the oven, let it cool, then taste it to determine if it has the appropriate texture.
Oven-Roasted In-Shell Peanuts
Rinse the peanuts to remove excess dirt.
Salt in-shell peanuts by preparing a simple saltwater brine that contains about 2 tablespoons of salt for every gallon of water. Soak the peanuts for 8 hours up to overnight. Drain the peanuts and allow them to dry.
Spread a single layer of peanuts on a rimmed baking sheet.
Place the baking sheet in an oven preheated to 350 degrees Fahrenheit.
Roast the peanuts for 30 to 35 minutes, checking for done-ness during the last 10 minutes. To check for done-ness, remove a peanut from the oven with a utensil such as tongs. Allow the nut to cool then crack it open. The inside of the shell should be slightly darker than the outside of the shell. Taste the nutmeat to see if the texture is appropriate. Peanuts continue to cook for a few minutes after you remove them from the oven, so take them out when the nut you taste-test is slightly underdone.
Oven-Roasted Shelled Peanuts
Toss raw shelled peanuts with peanut oil in a bowl, if desired. Add about 1/2 to 1 tablespoon of oil for every cup of shelled nuts you are roasting.
Season the oiled peanuts to taste with salt and any other seasonings you desire. Ground black pepper, chili powder and cinnamon are common additions. If you are uncertain about how much salt to add, wait to salt the peanuts until after you roast them.
Spread a single layer of peanuts on a rimmed baking sheet and place the baking sheet in an oven preheated to 350 F.
Roast the peanuts for 15 to 20 minutes, checking for done-ness during the last 5 minutes. Check by removing a peanut from the oven with a utensil such as tongs. Allow the nut to cool then taste it. Remove the peanuts from the oven when the nut you taste-test is slightly underdone.
Salt the peanuts to taste.
Prepare in-shell or shelled peanuts just as you would for oven roasting.
Spread a single layer of peanuts in a microwave-safe dish.
Microwave shelled peanuts on high for 10 to 12 minutes; microwave in-shell peanuts on high for 12 to 15 minutes. Stir the nuts every 2 to 3 minutes. Start testing for done-ness after 8 minutes. Remove the peanuts from the microwave when the nut you taste-test is slightly underdone.
Salt the peanuts to taste.