How you will create or help in creating a Product Roadmap?

The answer will vary from candidate to candidate based on their exposure and the size of organisation they are working in. For a small organisation the PO might be directly involved in creating the roadmap however in large organisation, he would be someone whose input would be required.
Typically the answer would evolve around : Continuous exploration – Taking feedback after every release , checking how the features has been perceived by the market, analysing competitor’s offerings and our customers’ reaction to it. Not doing upfront design and freezing the requirements. Having features variable for future releases and creating a roadmap which will follow Cone Of Uncertainty.