1)
What is "b'Ein Rogel"?
1.
Rashi citing Targum Yonasan: B'Ein Katzra (it is where launderers kick (Rashi Ta'anis 29b - trample on) wool garments [to clean them].
2)
What Shifchah told them?
1.
Radak: The Shifchah of Beis Tzadok went to Ein Rogel to tell them.
