Yes you have to root them before you can sex them out. Seems like kind of a waste of time to bother cloning males so I agree with Vostok but you can pull clones off young vegging plants to sex them after they are rooted. Once there are roots showing you can flip to 12/12 & see which are the girls to keep but this is only viable if the plants are mature enough for sex to begin with. Underage plants take longer to show so wait til they are vegged 6 weeks minimum from seed to take clones if this is your plan.