Optimizing the number of modules for a rooftop based of price and power output

Is it possible to get SAM to optimize the number of modules, and the distance between rows based on their price and annual power production given a fixed area on which the array is located (flat roof)?

It seems that the closest value to the area of the roof is the total land area, but it cannot be set and is calculated from other parameters. I need to be able to set the land area, and then find out what the best number of modules to put on it would be.

Thanks in advance.

I think you and I might be asking similar questions. I'm asking about "packing factor", which is one of the editable values in SAM. See here:
sam.nrel.gov/content/there-clear-explanation-packing-factor-option-solar-array-page