If all you want to do is re-route condensation dripping off the roof, and it's a rubber roof, one easy way is to buy a caulking tube of "Dicor" self leveling sealant for rubber roofs from RV dealer, and run a 1/4"-3/8" bead across roof from AC to wherever you want it to go, and let it cure for a couple of hours. Nobody sees it, and a tube is about $10 max.