The Steelmen racked up seven tries as they recorded their 17th win of the season, and have touched down an impressive 90 times in 19 games - 23 more scores than nearest rivals Bargoed.
First-half tries for Ebbw came through flanker Cameron Regan, full back Charlie Simpson and Regan's back row colleague Ronny Kynes, with outside half Dorian Jones adding a conversion and a penalty for a 20-0 interval lead for the visitors.
After the break scrum half Dai Jones, prop Josh Powell and wing Wes Cunliffe crossed the whitewash while Simpson added his second as the Eugene Cross Park side showed the dominance which has carried them all season towards a defence of their title.
Cunliffe's score came after a superb break from replacement outside half Dan Haymond, who also kicked three conversions. Hosts Rumney hold on to eighth place in the table on points difference.
Bargoed stay in contention with Ebbw Vale - at least mathematically - after edging to a 15-14 win over Blackwood at Glan-Yr-Afon.
They must win both their remaining games and hope Ebbw Vale lose all of theirs if they are to have any chance of pipping the Steelmen to the title.
Full back Andrew McLaughlan and flanker Gareth Davies scored the tries for Bargoed as they eked out the narrowest of wins over mid-table Blackwood. Outside half Jeremy Roberts scored a try and kicked three penalties for the home side.
Newbridge came out on top over Gilfach Goch in an entertaining clash between the league's third and fourth-placed sides at the Welfare Ground.
Gilfach led 13-7 at the break, but a three-try burst in the second period from the hosts saw them pick up maximum points for the sixth time this season. Newbridge's tries came through centre Dan Phillips, prop Geraint Weaver and replacements Geraint Langdon and Rhys Price.
In another compelling encounter Beddau left Merthyr with a 32-26 win over the Ironmen. Tries from wing pair Ieaun Coombes and Bradley Coombes, along with flanker Rhys Watkins, centre Lloyd Peart and replacement Abraham Papii secured the points for the Green and Golds.
Elsewhere, Mountain Ash edged a 22-20 victory over the Glamorgan Wanderers at Duffryn Pennar Parc.