short_circuit.rb

def parse_roles(user_hash)
  custom_schemas = user_hash.fetch("customSchemas") { return [] }
  roles = custom_schemas.fetch("Roles") { return [] }
  roles
end

user1 = {
  "email": "andrew@muvehealthlabs.com",
  "customSchemas": {
    "Roles": ["accountant", "admin"]
  }
}
parse_roles(user1)
# ["accountant", "admin"]

user2 = {
  "email": "nick@muvehealthlabs.com"
}

parse_roles(user2)
# []

user3 = {
  "email": "peter@muvehealthlabs.com"
  "customSchemas": {
    "Title": "Docker Jesus"
  }
}

parse_roles(user3)
# []