It's a real shame that salty snacks are so addictive, because you can be pretty sure anything that coats your fingers in orange powder probably isn't healthy. There are some exceptions to the rule, of course. Peanuts and tree nuts are relatively virtuous choices, with lots of protein and nutrients to offset their high fat content. It's always worth reading the label, though, because if you buy your peanuts pre-roasted, they may have a lot of additives and preservatives in them. If you can get raw peanuts where you live, roasting your own gives you more control over what goes into them.
Roast Them in Your Oven
If you're doing a big batch of peanuts, the simplest way is almost certainly to do them in the oven. It's mostly hands-free, it leaves your counters and stove free for other things, and your batches are limited only by the size of your baking sheets. Toss the peanuts with a tiny splash of oil and a sprinkling of salt first, which is optional but tasty. Spread the raw peanuts over a parchment-lined baking sheet or two, in a single layer. The actual baking part can go two ways, depending on your personal cooking style.
You can roast the peanuts at 350 degrees Fahrenheit for 20 to 25 minutes in the shell, or in about 15 minutes if they're already shelled. That's quicker, but you have to stir them regularly and keep a close eye on them so they don't scorch. Alternatively, you can roast them at 300 F for 35 to 45 minutes in the shell, or about 25 minutes if they're already shelled. You'll still need to stir them occasionally, but you'll have a lot more margin for error in case there are other things going on in your kitchen that need attention.
Roast Them in Your Microwave
For small batches, you might want to use your microwave instead of heating up the whole kitchen with your regular oven. Spread the raw peanuts in a single layer on a microwaveable plate. Start off by cooking them on high for two minutes at a time, stirring every time the microwave stops. After two zaps, you should start to see some browning. Cut back to 30 seconds, and zap them once or twice more. Your peanuts should be evenly golden brown. Any pale, under-roasted specimens can be discarded or go into your next batch, if you'll be making more right away. Start to finish, you'll be done in less than 10 minutes.
Roast Them in a Pan
You can also roast small batches of peanuts in a skillet or wok, which is more hands-on and surprisingly satisfying. It's not as quick as microwaving, though. Heat your skillet or wok over low to moderate heat. In a skillet, use enough peanuts to make a single layer over the pan. Keep stirring until the peanuts are evenly browned, roughly 8 to 12 minutes depending on the heat of your pan. Woks are curved, so you'll have to go by volume – a half-pound of peanuts is a good batch – and cook for longer, up to 20 or 25 minutes, so all of the peanuts can be fully cooked.
In either case, if you're stirring diligently but still see scorched spots, your pan is too hot. Slide it from the burner, turn down the heat, then wait a few moments before sliding the pan back.
Make Some Variations
The basic roasted peanut is flavored just with salt. You can add a pinch at the end, or if you're roasting your nuts in the shell, you'll have to soak them in a brine overnight so the salt flavor penetrates. For flavored peanuts, you have a couple of options. You can steep your favorite herbs and spices in hot water for several minutes, to make a sort of "tea," and then simmer your peanuts in the mixture for a few minutes so they absorb the flavor. If you're okay with added oil, toss your nuts with a tiny drizzle of oil and your choice of dry spices, before you roast them.
For honey-roasted peanuts, bring your honey to a boil and toss the peanuts until they're thoroughly coated. Toss the sticky peanuts in sugar with a pinch of salt, so they're easier to handle and separate, and transfer them to a parchment-lined baking sheet. Spread them in a single layer as best you can, and bake them at 300 F for a half-hour or so. Stir them two or three times, breaking up any clumps as you go.
Make Peanut Butter
If you've started this whole project with the idea of making your own additive-free peanut butter, you can start before the peanuts have even cooled. In fact, it works better that way. Put the warm nuts into the bowl of your food processor and pulse until they're nicely chopped. Next, run the food processor for a minute or so and then stop to scrape down the sides. The peanuts will look coarse and sandy at this stage. Repeat this process twice more, and your peanuts should be at about the peanut butter stage. Peanuts vary in their oil content, so if the butter is too stiff at this point, you can add some more peanut oil or any other oil you choose. Add a dash of salt, too, if you wish, then grind for one or two more minutes until you're happy with the texture. It won't be as smooth as commercial peanut butter, but it'll be spreadable and very, very tasty.