It was not denying an 'obvious goal scoring opportunity' therefore no he should not have been sent off. If he had, for example, stopped the ball with his hand as it was heading towards an open net, then yes that is a red card. Granted RL was just about to head the ball behind the defender but that does not consitute an obvious goal scoring opportunity since the ball was travelling sideways across the goal.
No need to thank me for clearing that up for you. Yellow card yes - Red card no.