I use to sell and install safes and vaults. I used 2 pieces of plywood, a J-Bar to
tip -up one end and place 3 1" solid bar stock under it. Let It down on them
and rolled it on the plywood always placing the back roller in front as you go along.
You can also pivot if you need to. Always roll it with the door towards you. When
you have it where you wany it, use the J-bar to tip it to remove rollers and plywood.
Like it has been mentioned, support your floor joist before you roll it to position.