With two wins safely under their belt, the side made light work of ma decent Ospreys side and even managed a bonus point to round off an outstanding season.
Stuart Maguire, James Leadbetter, James Thomas, Adam Hughes and David Langdon all crossed for tries with Jason Tovey adding to his points haul for the season with a brace of conversions and as many penalties.
Ciaron Ruddock, son of former Wales coach Mike, crossed for the Ospreys, but they were second best throughout an encounter that further confirmed the Dragons dominance this season.
In the other game, the Blues were 26-13 winners over the Scarlets at Abercynon. Home-town boy Dean Gunter kicked 16 points for the second successive game with Matthew Rees and Ben Morgan both scoring tries.
Centre Scott Williams and flanker James Davies were on the mark for the Scarlets with tries and full back Daniel Newton added a conversion.
