The simple answer is YES and NO! There are several variables. When I owned a roofing company I lived by direct mail but roofed in an area where roof sales where not storm related! If you live in a hail belt area they are not as effective, but can still work.
The economy is changing and like other market segments the roofing trade is not immune. As times change, so should your message. Currently, I use direct mail to drive business to my lead generation website. Post cards are the best avenue for two reasons; cost and readability. They are cheap to send and the customer is forced to look at it. That is why your headline is the most important factor.
All business owners marketing their company have to be aware of the marketing equation: Interrupt, Engage, Educate and provide a Low Risk Offer. If you remember that, you will have more success.
Below is a sample... In states like Arizona and California it worked very well. In a state like Texas, most advertising and marketing experts would call it; an utter failure. But, with that being said, I did sell one job from it, for which, not only paid for the mailer but made me a very nice profit plus it drove lots of traffic to my website. Remember, it only takes one job to have a successful direct mail campaign.

I used to look at response rate carefully, less so these days. I shot for 2% response on postcards and 50% closing rate, although I did a lot better than that.
These days I'm closing well over 80% of the jobs I bid and that jiggers the other numbers around.
References and referrals are our lifeblood and they make me a lazy "salesman." Below is text from a recent one, and the 2nd paragraph makes selling roofs a lot easier.
I am writing this letter as a reference for Adam's Roof Tech. ##########, L.P. has been more
than pleased with the service provided to us by this company. They are top notch in their craft. They go
above and beyond in all aspects of what they do. They installed a foam roof on the shop of our facility.
The insulating properties of this material are exactly what was promised. We also have a roof here on
the property that was installed by Tim in the 80s. Please don't hesitate to contact me if you have any
questions or concerns.
Good point- that was a direct quote from a call in. Also, depends on your audience. I did take a chance and use the quote and tested another less risky headline (but with the same design) and got "bupkis". It's all about testing before investing. Test! Test! Test!
The one project we did get out of it (see below) was from a frustrated property owner who was tired of people "Blowing Smoke up...." (You can finish the rest)- Now, I knew I could not put that as my headline! Again- it wasn't a huge project but paid for the campaign and we made some money.

Mixed results for us. Not nearly the 2% response we used to get.
As for mild profanity ("crap") in a postcard, I'd think that is a big no-no. A very shrewd businessman taught me long ago to never let our guys smoke around a customer. If the customer smokes and you do too, you will not offend him. But if he doesn't and you do, you very well might offend him. Same goes for using profanity around customers, or at least those you don't know well enough to know if you'll offend them.
The profanity adds nothing and will definately offend a percentage of the potential customers.