Moreno pushed the Italian when the two were in the middle of the peloton, approaching the foot of the Mount Etna climb. Rosa spun off the road and was forced to change his bike as a result.
Rosa said afterwards he was OK and uninjured and criticised Moreno for what he called "dangerous" behaviour.
"It was a stupid thing… I think everybody can see what happened on the TV," Rosa told reporters when he reached the summit of the climb, 78th on the stage and 13 minutes down. "It was a stressful moment of the race."
"If one guy pushes another guy out of the road and into the public, it's dangerous."
Moreno, initially 72nd on the stage, continued racing but did not make any comments to journalists waiting to talk to him at the finish line. He was later given a 200 Swiss Franc fine and thrown off the race for what the UCI commissaires' report called an "act of violence."
Now 32, Moreno turned pro in 2007 with the small Spiuk-Extremadura team. He has won a number of minor races in Spain during his 10-year career, most recently a time trial in the Vuelta a Andalucia-Ruta del Sol in 2015, but is best known as a mountain domestique. He crashed out of the Giro d'Italia last year with a broken collarbone and when he signed last year for Bahrein-Merida, said at the time that supporting Vincenzo Nibali in the Italian Grand Tour would be his big target of the season.