VEVOR Roll Roofing, 15 x 30 ft, 45 mil EPDM Rubber Roofing, Long Lifespan & Weather-resistant, Withstands Harsh Temperatures, Flexible & Easy Installation, Roof Underlayment for RVs, Roofs, Ponds

There is no safe adhesive method to mount this on an RV roof. This type of unit is not designed for roof installation and must be mechanically fastened to a proper load-bearing structure (bolts/frame) if installed at all. Adhesives (including epoxy or VHB tape) will not be reliable or safe due to vibration, heat, and wind loads while driving.

The iron bar, also known as flat iron, is fixed with steel nails or expansion screws.

You can hold the membrane down with something heavy or secure it with nails.