Lippert's roller tubes, like the Solera Rollbar for 19' 1" - 20' Long Awnings - Black # LC33FR that you mentioned are not going to be compatible with your Dometic Sunchaser Awning.
Since you're wanting to replace your roller tube, I assume it's damaged or inoperable, and in which case you'd need to replace the entire assembly with something like the:
-Solera Smart Arm 12V Power RV Awning - 20' Wide # LC517517.
This awning upgrade kit includes a brand new roller bar, awning fabric, and... view full answer...