Resuscitation of a newborn always begins with drying, gentle tactile stimulation, and proper positioning of the infant. In most cases, this will be sufficient to stimulate respiratory effort.
If a newborn has true respiratory depression, simply giving O2 (via blow-by or mask) will not suffice. If the kid isn't breathing, the concentration of O2 being supplied to him is irrelevant, because it is not getting into his lungs.
In the case of respiratory depression, PPV is needed, and should always be attempted prior to administering any drug, especially Narcan, because it is possible that the baby's respiratory depression is due to retention of CO2, and not the narcotics. It is never safe to assume that a baby is depressed simply because mom has recently received narcotics. In fact, most infants who are exposed to narcotics shortly prior to delivery have no respiratory depression at all.
So, to sum it up: 1. Dry, stimulate and position infant. 2. PPV for babies with respiratory depression. 3. Narcan is a distant third, and to be used with great care.