Can anyone clearly explain to me the value of RMS? Why would I want to give someone Root Mean Square data vs. Roughness Average or surface area data? Any help on this would be most appreciated.

The RMS roughness has an statistical value that the roughness average or surface area data don't have. The RMS roughness is nothing but the standard deviation of the height values contained in your AFM image. So it is a well-known statistical quantity that is used everywhere. Ideally, the RMS value tells you that around a 60% of the points of the surface have a height between average-roughness/2 and average +roughness/2, so it gives you a direct information on how smooth is your surface. The advantage with respect to the max-min height difference is that the influence of stray values or outlier points is minimized (one point in a million has a very small effect). However, there are some caveats if you care about the nitty-gritty statistical details (for instance, the RMS value is representative only when your height distribution function can be fitted to a gaussian. From a practical point of view, if your surface does not have huge steps or artifacts you don't have to worry). Roughness Average and surface area data are more ambiguous concepts and sometimes implementation- dependent. Surface area data gives you an idea of how convoluted is your surface, but even though I have carried out some hardcore statistical analysis of AFM images I have never found it of much use. Maybe others can give you more details.