Yes, your piano may be on casters, but they are only meant for pulling your piano away from the wall to so you can clean the back of your piano. (They are not designed to roll your piano across the room and down the hallway.) You may also want to vacuum underneath the piano after it is moved. If, and only "if" you have someone around the house who is strong enough to pick the piano off the ground, should you attempt to move it to clean.
In this case, show this person that there is a handle located about half-way up the back of the piano. Check that the handle does not spin or come loose. Have this person grab the handle with one had and get a grip underneath the keyboard in front of the piano. The piano should be lifted completely off the ground and moved about six inches from the wall. Keep your feet and your helper's feet away from the bottom of the piano for safety's sake. Now go to the other side and repeat the process, back and forth, until the piano is about three feet from the wall. The piano should be lifted off the ground so the legs don't crack or loosen under pressure.
Another option is to wait until your piano tuner comes and have them move it for you. Just have your vacuum cleaner and a dust mop handy. First, carefully dust of the back of the piano, or the sound board. Remove any foreign objects from down inside the piano, then vacuum the carpet or sweep the floor. Now move the piano back to its normal position which should be about two inches or so from the wall. You may want to ask your piano tuner what they charge for an internal cleaning and get this done the same day.
Remember, the same amount of dust that collects under your sofa, probably collects under and behind your piano. Who knows, you may even find those long lost family photographs or "McGyver" game cards that slid off the top of your piano many moons ago. What a "bonus!"