Yes and no, parboiling the potatoes before roasting will create a potato with a soft outside skin that will allow the seasonings to penetrate the potato. This process also is part of the cooking process so that they can be completed in the oven. While I love the results when parboiling, if you don't want to parboil, you can bake them longer to soften the potatoes completely through- about 30 to 35 minutes.