Rolls over Muscle coordination and perception are developed enough at 6 months for the infant to roll over. If unaware of this ability, the parent may leave the infant unattended for a moment to reach for something, making it possible for the infant to roll off an elevated surface. Sitting up unsupported is accomplished by most infants at 7 to 8 months. Crawling takes place around 9 months of age. Standing by holding on to furniture is accomplished by most infants between 8 and 10 months of age.