The closest mountains to me are about 5 hours away, and unfortunately where I live it is pretty flat. I realized between school and work I can really only make it to the mountains once a month. What is the closest way to emulate climbing, so I can build the endurance to climb? Tweaking trainer, rollers, working out? Ideas?

WIND! Lots of wind.

Also known as "Kansas hill training."

There are loads of hill training sessions for wind/turbo trainers.
Nothing beats hills but the indoor sessions can assist.

Try these 2 from the Training Routines thread.

Climbers 2 x 20
10 min warm up build towards E3
5min @ 95% FTP @ ~95RPM then change up 1 gear
5min @ 100% FTP @ ~90RPM then change up 1 gear
5min @ 105% FTP @ ~85RPM then change up 1 gear
5min @ 110%% FTP @ ~80RPM
5min Recovery then repeat
5-10min warm down

Climbers 45min long climb effort
10 min warm up build towards E3
5min @ 85% FTP @ ~100RPM then change up 1 gear
5min @ 95% FTP @ ~95RPM then change up 1 gear
5min @ 100% FTP @ ~90RPM then change up 1 gear
8min @ 105% FTP @ ~85RPM then change up 1 gear
7min @ 110% FTP @ ~80RPM then change up 1 gear
5min @ 115% FTP @ ~70-75RPM then change up 1 gear
5min @ 115% FTP @ ~65-70RPM then change down 1 gear
1min @ 115% FTP @ ~70-75RPM then change down 1 gear
1min @ 110% FTP @ ~80RPM then change down 1 gear
1min @ 105% FTP @ ~85RPM then change down 1 gear
1min @ 100% FTP @ ~90RPM then change down 1 gear
1min @ 95% FTP @ ~95RPM then change down 1 gear
5-10 min warm down

_________________
Don't let the truth get in the way of a good story......
Argon
CAAD9 6.78Kg
Supersix 6.78Kg

A very simple exercise is to push the hardest gear that you can do a smooth pedal stroke with. Take care to not work with our upper body at all, keep it totally relaxed, just push and pull the pedals. Focus on a round stroke. I've had some nice success with 3x15min and 5min of easy spinning in between. You can do this outside just fine, no need for indoor trainer.

_________________
Bikes: Raceur, Beateur