This is stacey from bitdeal- blockchain development company, I accept the previous answers have described the most common responsibilities of a blockchain developer, but now most of the blockchain companies are seeking much more efforts from a blockchain expert. So the, responsibilities have been diverted in to one more extra thing. (i.e) The current responsibility of a blockchain expert is, He/She would know the trick and methodologies to implement blockchain technology for industrial use cases, because blockchain has started to revamp many industries including, healthcare, banking, supply chain and etc. So, a blockchain expert would have capability to implement blockchain in these industries.