Early chances were exchanged at the County Ground in Letchworth, as Stevenage's Dominque Godber recovered brilliantly to block Sammy Tinsley's shot and then Fisher raced clear but Emma D'Costa saved bravely.
Royston's Georgia Gannaway found space in the box but her shot was saved by Katherine Long before the favourites broke the deadlock on 32 minutes, as Player of the Match Rosy Woodhams slotted home after great work from Bolu Fisher.
Four minutes into the second half, Godber doubled Boro's lead from a set piece and Royston almost replied immediately as Tinsley hit the post from 25 yards.
But Stevenage went three goals clear in the 55th minute, Woodhams doubling her tally with a simple finish.
The Crows kept on coming at Stevenage though but without reward, as Grace Leslie saw her powerful header saved, Harriet Smith got free only to be denied by another stop and later also clipped the post.
In the final minute, Stevenage skipper Donna McGuigan ran in the fourth goal to wrap uo the scoring.