Goals from Gavin Cogdon and Carl Finnigan secured what was a 10th consecutive win for the Mariners as they blew off the New Year cobwebs.
Both teams made a number of changes for the South Tyneside derby, with Roofing missing nine first-team players, while Shields rested the likes of Julio Arca, David Foley and Michael Richardson.
The Roofers proved difficult to break down, with Shields restricted to shots from distance in the opening stages.
Wayne Phillips was a persistent threat, and he fired a warning to his former club four minutes in when he went on a fine run before shooting over from 20 yards.
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Robert Briggs saw an effort from distance pushed away by Roofing goalkeeper Lewis Brass, and the closest the visitors came was when Calvin Smith curled a free-kick wide.
A number of half-chances came and went for the Mariners, before they stepped things up in the minutes before half-time.
Dillon Morse almost gave them the lead when he met a cross from Phillips with his head, but Brass got down well to keep it out.
That save only delayed the opening goal by two minutes, though, and it came as the Mariners countered quickly, with Phillips running through the Roofing half before sliding a pass through for Cogdon, who made no mistake.
It was Cogdon’s 14th goal of the season, and came on his first start in over two months after a groin injury.
In the second half, a save apiece from Brass and Liam Connell kept the score at 1-0 before Finnigan added goal number two for Shields a minute before the hour mark.
Jon Shaw’s flicked ball round the corner played the striker in on goal, and with the visiting defence waiting for an offside flag which never arrived, Finnigan found the bottom corner.
Shields went on to have their best spell, and Finnigan almost made it a quickfire double when he was denied at close range by Brass.
Substitute Stephen Ramsey was the next to go close as he fired wide after a good ball through, while Phillips saw a shot deflected behind after another strong run.
The third goal just would not come for Shields, though, and in stoppage time, Tom Bailey netted to give Roofing a consolation.
Shields can now concentrate on Saturday’s huge FA Vase tie with Morpeth Town at Mariners Park, while Roofing are at Marske United in the league, also on Saturday.
SOUTH SHIELDS: Connell, Nicholson, Holden, Phillips, Morse, Shaw (Baxter 77), Briggs, Scroggins (c) (Smith 46), Cogdon (Ramsey 62), Stephenson, Finnigan. Subs not used: Callaghan, Foley.
Goals: Cogdon (41), Finnigan (59).