flying DC to Vienna with return from Rome -- guidance on airline?

Try sidestep.com or kayak.com for options.

I'd also suggest that you check directly with United. Austrian Air is a star alliance member. I have flown direct between Rome and Dulles on United and also direct between Vienna and Dulles on Austrian Air. If you check United, select the "include star alliance flights" when you search. I think these are the best options for direct flights from Dulles. I am always willing to pay more for a direct flight. There will be many options for transfers if money is more important than time.

Nancy, I have found that orbitz gives a lot of information. I then go to the individual airline. Also, tripadvisor.com now has flight information.