I think roast potatoes with olive oil are fine. I brush the oil onto the potatoes which reduces the amount of oil. Alternatively you can buy an 'actifry' which uses very little oil but makes very good chips.
I usually have one or the other a few times a week and I am maintaining a lean body build. In fact with my exercise programme I need the carbs and good fats to maintain my energy levels.
So I think it can be fine to eat roast potatoes and even chips using an actifry.