If you are speaking of poker freerolls, they are pretty much a waste anymore. You will generally get a ton of freeroll whores that never deposit to fill the tables. Once the game is done they are on to the next freeroll.
I gave up on them about a year ago with the exception of hosting one for a new room I am promoting and then I only allow those of my forum members that are real players to join in. I have a "VIP" group of players that are ones that will play buy ins, play cash games or sit n go's and most important, deposit.
One thing you could try is to run a few low $ buy in games with an added prizepool and then have a freeroll for the players that played in the buy ins. That works a bit better. Another idea is to have a freeroll that only players that have deposited can enter. This removes the password, (and password thieving) and the poker room issues a ticket to those that deposit using your link/bonus code.
Most rooms will pay for the freeroll prizepool with the exception of FullTilt, PokerStars, Bodog (usually). Some will split the cost with you. It all depends on the room and the AM.
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"People who are unable to motivate themselves must be content with mediocrity." ~Andrew Carnegie~