Broadway producer returns to the stage BY PETER FILICHIA
In her role in the Roundabout Theatre's revival of the musical "The Boys from Syracuse," Lauren Mitchell plays Adriana, a woman in ancient Greece whose husband is off carousing with other women while she waits for him to return. She's described as "an angel," which is fitting -- for Mitchell has for the last five years been a Broadway angel -- i.e, a producer who's brought such shows as the current "Urinetown" and "I…