What is the difference between roasting and toasting?
The previous answer which says to toast something means to brown it is accurate. The difference between roast and toast is simple, really: roast means to expose something to dry heat (in the west, usually in an oven) and to cook whatever it is right through; toast means to brown the outside of something, either held over a fire (as in marshmallows) or placed under a dry heat source such as a grill or inside a toaster.

In practice, for your peanuts, its a lot easier to roast them than it is to grill them to get a toasted effect, but toasted should mean you put them under a grill and shake them about to brown them all over rather than 'cook' them right through. The risk with toasting under the grill is, obviously, burning - I've 'toasted' cashews in a hot oven by shaking them about a bit periodically for a short time, and I've also done it in a dry pan on the hob. The only time I did it under the grill, I burnt the lot...