Ooh, roasted potatoes...one of my favourite things!
The best way to get them crispy is to roughen them up first so the fat 'catches' the edges. I do it the traditional way in the UK and boil them first till they are just soft, then drain them off in a colander. I put a lid over the colander and shake them hard so the sides are sort of rough and fluffy. You can sprinkle a bit of flour over the top at this point if you like but I don't usually do this.
Then tip them into a tray (about a couple inches deep is best) that has been in the oven with oil in it till the oil is really hot. Baste quickly to coat the potatoes with the oil, season with salt, pepper, spices (I like a little cayenne) and put back into the hot oven. I cook them on 180C (not sure in F) for about 40 minutes but check on them every now and then, it depends on how much you make. I sprinkle on some mixed herbs just before taking them out.
This makes really crispy potatoes with a bit of crunch that are softer inside