In this paper we study the scaling of the surface roughness in regimes of smoothing and roughening. Transparent SnO2 films are sputtered onto rough glass substrates, and films in the thickness range 15-1200 nm are produced. Surface images are obtained by atomic force microscopy. Specifically we are able to determine the effect on the roughness exponent upon a transition from smoothing to roughening regimes, and it is found that the surface width scales differently in the two regions. To our knowledge this has not been seen before, and we are not aware of a theoretical explanation of this. For thinner films smoothing effects reduces the surface roughness as compared to the substrate, and the correlation length decreases. On the other hand, for thicker films the surface width increases with thickness again. For the thinner films the roughness exponent is in the range 0.5-0.7, and for the thicker films it is approximately 0.9-1. The growth exponent is found to be approximately 0.3.