Reynolds, in the final approach segment, typically, the ROC tapers from 200' feet to 500' at the FAF.
For a non-precision approach, using ICAO criteria, the final approach segment MOC (minimum obstacle clearance) is 75m, or about 250ft. The minimum obstacle clearance height is also 75m. The 'tapering' you are referring to is, I assume, the secondary areas? There the MOC goes from 75m to zero - ISTR this is different to TERPS , which I haven't looked at for some time.