There are so many places for them to hide, you need to attack this from many fronts. I have successfully rid one of our previous TTs from roaches, here is what I did.
Find those hard to reach places:
Under the shower tub
Under the sink
The furnace plenum
Under the refridgerator
Do the bottoms of your cabinets have a floorpan that can be removed?
Plan a time where you will not use the unit for about two weeks.
Remove all of the drawers, linens, dishes, silverware, food, and open the spaces I mentioned above if possible. Turn off the propane (all pilots out) and disconnect the electrical. Shut all of the vents and windows.
Set off 2 or so of the roach bombs (the aerosol kind, we used Hot Shot) inside the unit. If you have any large external compartments, toss one in there also. Vacate and close. Wait a week. There will be dead critters all over when you reopen. I followed up by putting bait paste under the compartments before replacing them.
Wipe and clean everything thoroughly afterward.
This worked for me.