bitcoin-cli signmessage 19Mz2o9RDABT74SA9njZqMtJXKEzj2qUoH '@RogerVer lets make a deal, 1 for 1 trade. At least 60k, possibly up to 130k, my BTU for your BTC.' H9ed6z5RgdThRxXXqePmtJbaK1pGvoy6e+aiwUPD6pkrJ6d6TBchOu5OQLEbgq/15YRjcOUC+kMrGVfszUXV5Wc=
Who cares if he didn't sign it. Obviously its him unless you believe someone hacked his youtube and bitcointalk account.