Solar panels

Yes. A lot depends on what the panels have. Is the charge controller built into the Jackery or is is separate? If it is separate (or attached to one of the panels), is it fused? As for using it in conjunction with the one on the roof, it sounds like you have a charge controller. I'm going to defer to Offgrid for this, since he is the subject matter expert here. He can give you the particulars.

All solar modules are made up of strings of solar cells, with each cell producing about 0.5Vdc. The total voltage the modules produce is proportional to how many cells are connected in series.

So yes you should be able to use your Jackery solar modules to directly charge your trailer battery. You will need to determine the solar module voltage though so you can get the proper charge controller.

Doing that direct connection is a good idea as that will be much more efficient than indirectly using the modules to charge the Jackery battery, then discharging the Jackery battery through it's inverter, only to convert the Jackery 120Vac output back to 14-15Vdc via the rpod WFCO converter to charge the 12V battery.
   

So the first thing you need to do is determine what voltage the Jackery solar modules produce. If you either have the specs or model of the solar modules that came with the Jackery system, or using a multimeter you can measure the voltage produced by the modules (when placed in direct sun of course) that would be enough to tell what's needed. If it's around 17-18Vdc (pretty likely) that is a typical solar module designed for 12V battery charging and any standard PWM type charge controller capable of handling 200 watts will work. If it's a higher voltage you'll need an MPPT type controller to step the voltage down.

You will also need to either get a mating connector for the ones of the Jackery modules so you can connect them to the charge controller, or cut off the connectors and replace them with new ones of your choice, taking care to keep track of you polarity of the connections.