I know that non-Israel grown raw peanuts in their shell are considered plain "vegetables" / legumes and do not require kosher certification, as other untouched fresh fruit / veggies.
Shelled peanuts roasted in oil do require certification, as these go through some manufacturing processes where eitherthe oil itself may not be kosher or something unkosher may be in the processing plant that came in contact with the peanuts.
What about the roasting process if the peanuts are still in the shell? I heard that no oil is used in this process - they are heat roasted. I don't know if most places use a dedicated oven that just roasts peanuts. Furthemore, I had heard that since the shell is not eaten and nothing penetrates the shell, anyway, there wouldn't be a concern even if it came into contact with something non-kosher.
Can anyone verify this claim regarding unshelled roasted peanuts?