Commercial Ross rifles have flat crowns. By way of example, Commercial Mk II** target rifles have flat crowns while Military Mk II** target rifles have the rounded crown. It would be interesting to know how an HG rifle ended up with a flat crown.
This is true for commercial rifles built on the 1905 action.
Commercial rifles based on the M-10 action (M-10, E-10 & R-10) have a rounded crown.