The oils I have on hand (not counting an old bottle of sesame oil in the fridge):
EVOO - used mainly for drizzling and vinaigrettes
Light olive oil - used for most of my pan-frying and oven roasting
Grapeseed oil - used for when I need a neutral oil (I think the one I have is actually a blend of grapeseed and canola oils)
Peanut oil - high-heat pan-frying, making popcorn on the stove, and deep-frying
As to lard and duck fat…I’ve made and have had made potatoes roasted in duck fat many times, and truly don’t get the appeal. They’re fine, but people wax on and on about them like they’re something from Heaven’s Own Kitchen, but they’re no better or worse than any other roasted potatoes I’ve had.
When I’m roasting potatoes, it’s usually done with a big hunk of bacon grease/fat and a little light olive oil.
I also frequently double up on types of fat, usually some kind of oil mixed with either butter or bacon grease/fat.