Requesting specific room can be done but it is the least likely request to be met. If you make a location request, and they cannot meet, the default is to put you anywhere in the resort that is open and not try to find something close to what you want. Thus, requesting a specific room could result in your being as far away from that room as you can possibly be at the resort.
You should instead request something more expanded as to a location. In your case, you could request sunset savanna view and close to the Rafiki elevator (down that elevator to ground floor gives you shortest possible walk at the resort to an entry gate to the pool area) or just close to pool. You could also add lower floor (the "lower" floors are 2 and 3).
The requests should be made through Member Services and then when you do online check-in you should skip the request page in that process. The requests offered are more limited than you can make through MS and if you use that request section, your MS requests will be overruled. If you are renting through Disney, you may be limited to the type of requests offered on that check in page