Although it can be done it is not always advisible. Pianos weigh anywhere from 400-800 lbs and without a proper piano moving dolly and a piano board (in case of stairs) the move is going to be difficult and dangerous.
Casters on the piano are for moving the instrument a few inches in place, not rolling it across a sidewalk. The typical cost to move a piano for our clients in New York City ranges from $200 for a small upright in two elevator buildings, to more for more complex moves.
Do yourself a favor and hire piano movers, you will be glad you did.