Ask a Neurologist. Get Answers to Your Neurology Questions.
The medication in Prozac tends to linger in your body, because of it's long "half-life", which means that your body metabolizes the medication slowly.
So, it may be a couple of weeks before your body metabolizes 95+% of the medication, and so if your new symptoms of RLS are related to a side effect of the medication, it may be another few days until these symptoms dissipate.
Of course, it is difficult to know if the medication is directly related to your symptoms, though if the symptoms started only with the medication, then it seems likely.