Yes, they can be adjusted. On my rig, you have to pull the valances to get to the adjustments. I gather you will do them regularly as they age, roll, and unroll.
The good news is that if something breaks repair parts are available. I had two with broken springs.
Aaron
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2014 Itasca Meridian 34B 2016 Coachmen Concord 300DS
2015 Focus Hybrid following along