With levers and rollers you can do a lot, without lifting, if everything is at nearly the same height.
If you need to raise a timber up off a cart onto saw horses alone, then you may need to create a set up where you tip the timber one way and insert a spacer block then tip it the other way and insert another spacer block and keep doing this until you raise the timber up. Of course you'll need to have a good base.
Watch this video if you can it shows what I mean:
http://www.youtube.com/watch?v=lRRDzFROMx0
