Every object in EnergyPlus has a specific list of output variables that it can report. For the Material:RoofVegetation object, that list of output variables includes:

• Green Roof Vegetation Latent Heat Transfer Rate per Area [W/m2] : Latent heat flux from vegetation
• Green Roof Soil Latent Heat Transfer Rate per Area [W/m2] : Latent heat flux from ground surface
• Green Roof Soil Temperature [C] : Temperature of the Soil layer temperature
• Green Roof Vegetation Temperature [C] : Temperature of the Vegetation layer temperature

The Material:RoofVegetation object is used to represent only the layer of soil and vegetation. To include a layer for a substrate, you will likely need to include a Material object or something similar in your input file, and then reference both of these with any other roof layers using a Construction object.

To generate output variables from EnergyPlus models, you will need to add Output:Variable objects to your input file. Refer to other posts HERE and HERE related to adding output variables to EnergyPlus models. It seems that you can report inside and outside face temperatures for an entire surface, but not temperatures inside of a construction assembly defined by Material objects (other objects like MaterialProperty:VariableThermalConductivity and MaterialProperty:HeatAndMoistureTransfer:ThermalConductivity can generate output variables for temperatures inside of a construction assembly).