That sounds like a band-aid fix for a slide out roof that has been damaged by water intrusion.....otherwise why is it sagging.
Correct fix would be to remove slide out and replace roof with new wood and find/fix area where water seeped in.
Have you contacted your INS. Company, had an adjuster check it out?
We had to have the floor replaced in our slide out.......insurance covered.
Took a week for material to be shipped from mfg. and then 2 days for repairs (remove trim, disconnect electrical, remove slide out, tear out floor, install new floor, re-install slide out, hook up electrical, re-install trim, caulk and let sit overnight to cure)