I don't understand if you're asking about placing a roommate ad on Trulia, or if getting a roommate is a good idea...
No roommate ad on Trulia.
A roommate to share your present expenses to allow you to save money for a down payment is a good financial plan. Whether or not it will "work" in the real life day-to-day may be tricky if you can't find the perfect match.
Best of luck!