I don't see anything wrong with your basic set-up. The cockerels get up there on their own, so it is not like they can't use the ramp. They could fly up there without the ramp if they wanted to. Do not get hung up on the ramp. The ramp is not the problem.
Have you tried leaving them locked in the coop portion only for about a week? Do not let them in the run at all for that time period. They need to get used to the idea that the coop is where they spend the night. That is the first thing I would try. It does not always work, but it is an easy thing to try that will often work.
Sometimes the coop is too dark. That's where the talk of the light comes from. They cannot see in the dark, so if the coop is too dark for them to see in while it is still fairly light outside, they cannot see to go to bed in the dark. Windows or a small light in the coop can help. A light outside can hurt. Just something to consider.
Nine weeks is an in-between age. Most of my brooder raised chicks do not start roosting before ten weeks, though my current batch started at 5-1/2 weeks.
I have had chickens not want to go in the coop because other chickens were being vicious to them on the roosts, but at nine weeks I would be surprised if that were the problem with two cockerels. Usually at that age, the girls are beating up on the boys as much or more than the boys beating up on the girls. Still, dont entirely rule it out.
Are you sure you are waiting for it to get dark enough for them to go to bed? Sometimes the ones lower in the pecking order wait until the last second to go to the coop so the others wont pick on them so much. Ive noticed that mine can be pretty vicious at bedtime in enforcing their pecking order rights.
I had a group that the first day they were allowed in the run, about half went to bed in the coop and half stayed in the run when it got dark. I put the ones in the run where they needed to be and the second night they all went into the coop. It may be that they just need a reminder or two.
Hopefully you will find something in here that helps. Good luck!