Since we are using a terrain-following coordinate system, it is often necessary to smooth the bathymetry in realistic applications. ROMS reports two metrics for "Maximum grid stiffness ratios". We try to keep rx0 at 0.4 or below, this being something we can compute based simply on the grid file before running ROMS. For rx1, Sasha has this to say:
"rx1" up to 3 is considered "safe and conservative"; less than that value usually means that you smooth your topography too much in a realistic application; In practice we often run model having maximum values up to 5 or 6; above that you have to use more caution. Values exceeding 8...10 are considered "insane".