I don't usually have bacon fat on hand anymore because of kashrut, but with duck fat, I would melt the fat, then toss the potatoes with it and with whatever herbs I wanted to add if any (thyme? salt and pepper for sure), and then roast at 450 for half an hour, then stir, reduce heat to 350, and roast another 15 min or so until potatoes are tender (depending on size.)