There are two parts to what you are referring to as "Ratzon": One, the fact that you want something to happen; and two, the reason that you want it to happen. When we say "Ratzon" in regard to Hashem, the word means "want" only with regard to the first part. Hashem wants certain things to happen and others not to, but the other part of Ratzon, the motive behind our wanting certain things to happen, does not apply to Hashem.
Whereras our "wants" are always the result of some benefit that we gain if what we want comes to fruition, Hashem "wants" things only because we gain by it, not Him. We call his Ratzon "רצונו הפשוט" which means a Ratzon not because of any underlying need. Hashem's Ratzon is Ratzon without any need to cause that Ratzon. The only reason Hashem ever expresses any "Ratzon" is for the benefit of others; not Him.
Enlightening. Thank you Rabbi Shapiro!