I read up on Examine.com mentions a study which found that oral dosing of Rhodiola Rosea produced no appreciable effects on MAO, despite boosting Serotonin. Referring back to the original study which documented the MAO inhibition of Rhodiola, there is a clear difference between the type of extracts used.
So I wonder if this property will only exist for certain forms of the extract, namely the water and alcohol extracts (both which produced inhibitions above 80%).