Island dominated growth in cobalt/ruthenium structures is used to create films with varying degrees of structural roughness. The resulting magnetic films constructed in this way are continuous thin films with a distribution of islands on the surface. The size and spacing of the islands are remarkably uniform; and the degree of roughness is determined by varying the thickness of the continuous film relative to the density and size of the islands. The evolution of coercive fields, saturation fields and remanence are studied for differing degrees of roughness, and particular attention is given to consequent effects on domain pattern formation and stability. The stability of the stripe domain pattern is sensitive to the island structure, and strong correlations are found between domain pattern stability and film structure. Two types of behavior are found and the transition region between these behaviors is studied experimentally and theoretically in terms pf stability to effects of roughness. A scheme to distinguish between randomly and regularly distributed defects based on measuring stripe domain quality is suggested.