The trick is to boil the potatoes first. The recipe calls for small potatoes but I have instead cut down full-size potatoes after boiling too. Once the potatoes are soft (and cut down to size if needed) I toss them into a baking pan, pour some oil, add coarse sea salt, lots of rosemary leaves, and then mix it up. I toss the pan in the oven with whatever I'm already cooking in there <30 minutes before I expect it to be done. Of course this timing is pretty flexible (20 minutes is also fine).
... Joan made me do it.