I am planning to join the RS Bulgaria tour that starts 22 September 2013. I would like to arrive a day or 2 before the tour and maybe stay a day after the tour ends on 3 October 2013. Then fly directly from Sofia to Rome and stay in Rome for a couple of days. Then fly back to San Antonio with as few legs as is possible. I am willing to pay $500 more to skip a leg; if it cost more than that, I would have to think about it. It is my understanding that there are not daily flights from Sofia to Rome. Has anyone already been there, done that and be willing to advise of what things I need to be aware of before I begin my ticket search? (James, formerly of Helotes?)
See if I am following You want to fly to Sofia from San Antonio, then Sofia to Rome, Rome to San Antonio. A three leg flight? Use the multi-city option, plug it in and see what happens. Unless I am misunderstanding your question, there nothing to be aware of just use one of airline search engines. Play with a few dates and see if that changes the air fare.
You might try SkyScanner.com. It lists some flights that may not show up in other airline search engines. Good luck!