The application of hybrid composites in lightweight engineering enables the combination of material-specific advantages of fiber-reinforced polymers and classical metals. The interface between the connected materials is of particular interest since failure often initializes in the bonding zone. In this contribution the connection of an aluminum component and a glass fiber-reinforced epoxy is considered on the microscale. The constitutive modeling accounts for adhesive failure of the local interfaces and cohesive failure of the bulk material. Interface failure is represented by cohesive zone models, while the behavior of the polymer is described by an elastic-plastic damage model. A gradient-enhanced formulation is applied to avoid the well-known mesh dependency of local continuum damage models. The application of numerical homogenization schemes allows for the prediction of effective traction-separation relations. Therefore, the influence of the local interface strength and geometry of random rough interfaces on the macroscopical properties is investigated in a numerical study. There is a positive effect of an increased roughness on the effective joint behavior.