I don’t know what your set-up looks like, how big your coop and run (if you have a run) are, or how you manage them. My set-up is not with separate nests but there are people on this forum that do have the nests separate, usually at the far end of a run. From growing up on a farm with free ranging chickens where some slept in the coop, some slept in trees, and occasionally some might sleep in the hay barn, having separate nests and roosts can work. They did not all lay in the coop either. As a kid I had a lot of fun trying to find some of those nests, but that was because they were free ranging, not because the nests were separate from the roosts. Most that slept in trees or the barn would still lay in the coop.
You may or may not have to train them to use those nests. Some of that is going to depend on your set-up, some on luck. Having separate nests and roosts doesn’t necessarily mean they will use the roosts and nests as you intend either. They may still want to sleep in the nests. As Aart said, having the roosts clearly higher than the nests helps, especially when they are side by side, but you may still have to train them to use the roosts and maybe the nests.
In Guam you certainly are not worried about cold weather for your chickens. You can have a really open set-up which means your coop can be mostly wire which is less expensive than most of us on the mainland need to use. Hopefully your coop is all enough that you can get vertical separation.
Good luck!
