Is it ok to install a dryer vent in the roof of an old 1970 trailer?

I am having problems with moisture in my bathroom where I have installed a washer and dryer combo (built all in one). I am presently using a vent with a water box attached (the kind you use when you do not have a vent). I would like to know can I vent to the roof and how do I do this project, or how can I handle the mositure problem. Is there other ways to vent to prevent the mosture problem. Any help is appreciated.

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