I have done roof water leak repairs on two trailers. One was a complete roof replacement including boards, and other was a front corner where I had to peal back the roof membrane. Once water gets under rubber roof, it will peal back very easy.
I would first recommend that you have someone put a tarp over the roof to stop the water from getting in. With RV leaks it is what you can not see that is the big problem.
With past trailer I started by taking out damaged ceiling and wall paneling first to get scope of work from below before having to open up roof to replace damaged roof joist or studs in walls. First you will have to take out cabinets for access.
On the top side you will have to take off roof edge trim strips at front, and down side to be able to peal back roof. You will then be able to see any structural damage to wood joist. After replacing damaged wood I cleaned under side of roof membrane with a wire brush, and applied roof contact cement to repaired roof and underside of membrane before reinstalling it. You will need new putty tape to reinstall strips and Dicor Roof sealant.
This is the basics of repair, send me a PM if you need more information.