There seems to be no consistent height for the connection point between roads and level/grade crossings - certainly the UK ones I use. With many roads, when connectd to the crossing the last few metres of road disappear below surface level and it is very difficult to find a compatible road - at least, one that I like. I must have recourse to TACS/Gmax and do some experiments!
However, my 'fix' for this problem is to lay the road to within a short distance of the crossing, then connect it with a length of 'invisible' road. I then finish it cosmetically with a length of the same road which is not connected to anything. With care, a realistic result is possible - and the 'free' road spline point can be height-adjusted as needed. The level/grade crossings respond as normal to approaching trains.
Ray