overridden_id.rb

require 'byebug'
require 'rom-sql'

rom = ROM.container(:sql, 'sqlite::memory') do |conf|
  conf.gateways[:default].create_table(:users) do
    primary_key :id
    column :name, String
    column :created_at, Time
    column :updated_at, Time
  end

  conf.relation(:users) do
    schema(infer: true) do
      attribute :id, ROM::SQL::Types::Int
      primary_key :id
    end
  end

  conf.commands(:users) do
    define(:create) do
      result :one
      register_as :create

      def set_timestamps(tuple)
        tuple.merge(created_at: Time.now, updated_at: Time.now)
      end
    end
  end
end

puts rom.commands[:users][:create].before(:set_timestamps).call(name: 'Chris').inspect
# {:id=>1, :name=>"Chris", :created_at=>2017-01-12 18:25:22 +0100, :updated_at=>2017-01-12 18:25:22 +0100}