While it isn't Roger standing there with a signed declaration written in his own blood at the time of his death that he had no DF(jks) - It does make me a little less enthusiastic towards that theory. However that is just a moment in time - also WB was active duiring this time and it seemed to be common knowledge he had the Earthquake ability .... just not to us.
So further lending support to people in the One Piece universe being known for their Names - not their powers. I'm not as sure Roger had the Gomu fruit but I am not discounting it either - too many similarities are popping up for me to consider it unlikely.
Because there are no legends of him stretching or using it?
Remember SA Human Auction House - the 3 Captains with the Largest bounties fought together and Neither of them knew the others abilities - Also remember Roger destroyed those he fought with.