Is this for your rubber roof?
I have learned a new roof cost around 4-6K to install. Upon research and IMO liquid roof is a better product. Its essentially a new roof put on before the old one is beyond repair..
Its around $500 bucks for 4 gallons that covers 180 sq ft...
Like I said...just my opinion, but my RV roof is in good shape for 10 yrs but I am going to do use this next yr after the winter.
http://www.liquid-roof.com/liquidroof.html