In my state, people who go to precinct meetings have no say who ends up on the ballot either.
In New York, the county party chairmen get to decide who goes on the 3allot, and it's similar in PA. However, they rarely keep people off and even if they say no, you can collect a few signatures and get on anyway.
The RNC can provide resources to candidates - and that's a3out it. Almost everyone over there left to work on Romney's campaign - it didn't help him at all.