Let's start with LCO. You need to be able to flip two switches at the same time, know when it's safe to flip the switches and be able to read from the flight card. The first two are important. You don't have to be good at the third. I can train you at a launch in five minutes.
For the most part, anyone who has flown rockets for a few years can do the RSO job. You need to have a good idea of what works and what doesn't. Motor on the bottom, at least three fins on the same end of the rocket as the motor, balancing just forward of the fins and some kind of launch lug covers most model rockets. It's always good to ask a flyer you don't recognized if there's non flammable wadding. If the flyer hesitates when you ask him a question it usually means he's clueless and you have to look a little more carefully. High power needs a little more scrutiny. Common failures include inadequate shock cords, improperly wired or programmed electronics, poor motor choice, and improper motor assembly. These can be hard to catch at check in and if you don't like the answers your getting you can ask the flyer to disassemble the rocket in front of you. It's not unreasonable to ask to have the location of the CP and CG demonstrated. If you have any doubt you can ask a more experienced flyer for a second opinion.
The LCO and RSO have total authority over what flies and what doesn't. If either/or have any question about the safety of a flight the rocket does not fly.