The real Rose Hovick (b. August 31, 1890) was 20 when Louise (b. February 9, 1911) was born and 22 when June (b. November 8, 1912) was born. The girls are 7 and 5, respectively, when the story begins (somebody correct me if I'm wrong), which would make Rose 27. I assume the play ends with Gypsy in her early 20s, making Rose in her early 40s. Thus, she should be no older than 45 at most.
You can get away with casting older on stage, since the audience is generally far away and the lighting helps, but the camera is up close and personal and not as forgiving. The two movie Roses, Russell and Midler, were 54 and 47, respectively. That's still in the ballpark of 45. Streisand is nearly 20 years older than Russell was, and 30 years older than Rose was in the story! Heck, she's a decade older than Rose ever was; she died in 1954 at age 64.
Salve, Regina, Mater misericordiae
Vita, dulcedo, et spes nostra
Salve, Salve Regina
Ad te clamamus exsules filii Eva
Ad te suspiramus, gementes et flentes
O clemens O pia