Fullback David Johns and scrum half David Cavin also got a try each. Roberts successfully kicked two more of the conversions and a penalty to take his personal tally to 11.
Wing Danny Clemence and fullback Gareth Bowen got two of the tries in reply for Rumney, the other coming from outside half Danny Clark, who also kicked a conversion and a penalty.
Scrum half Ross Lucas and wing Gavin Close each grabbed a brace of tries as Rhydyfelin put 52 points on Abergavenny in Division Two. Kirk Richards, Mark Taylor and substitute wing David Gratton got the other tries with fullback Ceri Cummins kicking five conversions.
Llantwit Fardre lost 15-24 at home to Ynysybwl in the other game in Division Two.
Cwmbran keep the pressure on Newport HSOB in Division Three with a 14-20 victory away at New Tredegar. Outside half Carl Moore helped himself to 15 points with a try in each half, a penalty and a conversion.
Anthony Hayes and Andrew Thomas scored tries in reply for New Tredegar with Alex Davies converting both touch downs. A Sean Watkins try was enough to give Cwmbran a six-point lead and ultimately the victory.
Fourth-place Pontypool beat second from bottom Brynithel away from home 7-34 as they look to put together a strong finish to their season.
Abercarn picked up their first point of the season in Division Three at home to Senghenydd in a 15-15 draw. Senghenydd are the only team in the division to have conceded more points than Abercarn this season, with a points against tally of 780.
Garndiffaith stay top of Division Four with a 20-48 win away at mid-table Llandaff. Old Illtydians remain in second in Division Four with a hard-fought away victory over Tredegar Ironsides.
Lee Fletcher produced the outstanding display of the day in Division Five. His hat-trick of tries converted by Matthew Anderson put Bettws on course for a 35-25 win at home to Ynysddu.
In Division Five South East Deri beat third-place St Albans to record only their third win of the season.