We give a simple explanation of recent experimental evidence that ice crystals may grow in water vapor at low supersaturation (i.e. under atmospheric conditions) without screw dislocations. Examination of the intermolecular potential shows that by assuming non-bulk-like orientations, dangling molecules at surface-cluster edges may form strong hydrogen bonds with substrate molecules. This leads to a study of ice surfaces within the framework of an Ising-like model in which molecules with nearest neighbor vacancies which can provide vertical bonding are allowed two distinct states, yielding bulk-like as well as reconstructed monolayer ledges. The surface roughening transition is examined for this model by means of (i) a Monte Carlo determination of critical points and (ii) an analytical treatment of nucleation clusters. It is found that rough surfaces and, correspondingly, (dislocation-less) surface nucleation growth, prevail at temperatures below the bulk melting point over a wide range of feasible binding energies.