Room requests are exactly that:  a request – and can’t be guaranteed.  It is recommended that guests list their preferences for room locations during the initial reservation process.  Your requests will then be documented on your confirmation paperwork and within the information later forwarded to the appropriate resort.
If you use online check in through the My Disney Experience App, you’ll be able to make certain requests at that time.  Available options will be presented to you and you may check off items of importance.