Thermal conductivity and bulk viscosity coefficients are studied in the state-to-state approximation to assess the importance of accounting for rovibrational coupling and increasing diameters of vibrationally excited molecules. Transport coefficients are computed in binary mixtures for a wide temperature range, and compared to those obtained for the rigid rotator model. It is shown that accounting for rovibrational coupling leads to a twofold decrease in the bulk viscosity coefficient and a 5–7% decrease in the thermal conductivity coefficient; accounting for variable diameters has no effect on the bulk viscosity, but leads to a larger decrease in the thermal conductivity.