I think perhaps you used too much flour in the dough or your overworked the dough. This dough is supposed to be quite soft, so don't add all the flour at once. You may not need all four cups. Because you are making a light, cakey dough, you only need to knead the dough once at the beginning, and only for about 5 minutes. If you cinnamon rolls are dry, but still edible, just add more icing to make them a little more palatable and make sure to serve them warm.