Materials with dynamic surface topography may enable a variety of new technologies from smart coatings to biomaterials with controlled cell-material interaction. However, current approaches to create morphing surfaces require programming procedures, either before or after polymerization, that complicate the application of these materials. Here, we exploit the metastability of the microstructure of semicrystalline polymer networks that crystallize while photopolymerizing to create polymer coatings and microstructures that irreversibly morph from smooth to rough in an emergent manner when heated. For example, a smooth polymer coating with a root-mean-square (R-q) roughness of 15 nm transforms into a rough film with a R-q roughness of 688 nm on heating through the melt temperature. We show that this behavior is observed across a range of polymer networks and that the degree of undercooling during polymerization is the primary factor that controls the magnitude of roughness. This technique is not limited to polymer films; microstructures fabricated utilizing micromolding or emulsion polymerization also undergo changes in roughness on heating. Finally, we discuss using this approach to create polymer structures with spatiotemporal control of coefficients of friction and contact angles.