This article is from the Recreational Figure Skating FAQ, by Karen Bryden with numerous contributions by others.
Although inline skating can be an excellent exercise for overall
fitness and some basic skills can transfer well to the ice, more
advanced figure skaters find that regular inlines are rather
unsuitable to practice advanced freestyle maneuvers. If you are
determined to do freestyle off-ice, consider purchasing Picskates or
Triax skates. They both have a toe-stop at the front which makes it
easier to jump. Triax skates seem to be more popular with former
roller skaters, while Picskates, with their rockered profile, are the
ones that most closely resemble an ice blade. Having said that, be
aware that most things will be harder to do on Picskates than on ice
and a few skills, like spins, are considerably harder.