I shoot at a large private facility with a lot of different ranges (BP, 100 yard, 200-300 yard, indoor .22, bullseye pistol, practical pistol, etc....). During the week the entire facility is patrolled by a volunteer "range officer". They do not physically controll any individual range but are there to make sure everything is going O.K. and to deal with any problems (like people sneaking onto the range). Individuals on the ranges are responsible for keeping things safe IAW the rules pertaining to that particular range.
During more formal competitive shoots (usually on the weekend) each discipline tends to have RO's present who run the show for the competition in question.
When we have "hunter sight in days" there are RO's all over the place and the rifle range being used is tightly controlled (PA system, flashing red lights, chamber flags, etc.)as these sessions are open to the public and you can get some real dip^%#s.
As to training and certification, the patrolling RO goes thru an indoctrination period so they are familiar with their duties. Individual disciplines (IPSIC, CAS, etc.) have their own
RO certification program.