MP7.5 Simple answer is max throw on elevator (my ROO has approx 3/4") and minimum throw setting on low rate aileron 1/4" deflection is safe. This is a good starting point as ailerons are very responsive and can catch you out on take off if you are not ready eg forget to switch to low rate.
You could always adjust sensitivity via expotential as an alternative.... I find you cannot have to much up elevator throw on a ROO.

Not sure as to differences between elevon vs aileron/elevator on the ROO as I have only used the elevon style set up. I would say that ailerons/elevator set up would be less sensitive. I would use similar settings though until you log some flight time and get confident...