Yes, all teeth have roots. But when they fall out naturally they don't have them anymore. The "big" teeth below "disolve" the roots by pushing the baby teeth out.
about 20 they start coming out at about 6 moths. they will all fall out bout when your 14 or 16, and replaced by permanent teeth. http://www.intelligentdental.com/2010/02/22/dental-care-for-babies/