While I would have preferred it to have been Cate Blanchett, I think Julia Roberts will be fine. She is a little miscast, but she will pull it off. The one thing from the show that obviously can't be recreated is the marvellous visual conceit of moving all the props to the back of the stage at the end of each scene. By the final scene, the stage was full and the actors were performing among the debris of the earlier scenes. This gave powerful resonance to Anna's earlier line about baggage.
Nothing precious, plain to see, don't make a fuss over me. Not loud, not soft, but somewhere inbetween. Say sorry, just let it be the word you mean.