JAMES Roberts had a debut to remember as Oxford United produced a professional and eye-catching performance to reach the second round of the FA Cup at Grimsby today.

The 18-year-old, who signed a new four-year contract 24 hours before the match, scored a first-half double on his first start as Michael Appleton's side ended a run of two successive defeats.

Danny Rose scored the third goal five minutes into the second half, but the day belonged to Roberts.

Having come off the bench in the last five games, Roberts had earned a first start.

And he grabbed the opportunity with both hands in an outstanding display.

His first goal on 35 minutes showed pace, control and precision. His second, seven minutes later, showed predatory instincts and a cool head to side foot home from six yards out.

The only negative for United was a goal from Shaun Pearson with ten minutes to go, meaning the U's are still to keep a clean sheet on their travels this season.

But the main thing was getting through, and that's exactly what they did.

Appleton made three changes from the side that lost to Wycombe Wanderers last week, one of which was forced.

Danny Hylton's suspension gave Roberts a start, with Brian Howard and Callum O'Dowda also named in the starting XI at the expense of Tyrone Barnett and Michael Collins, who dropped to the bench.

Roberts began well, showing nice touches and a willingness to close down the home side.

Both teams started well enough, but a greasy surface and strong wind meant several passes went astray.

When the match settled down, it was the hosts who went oh so close to breaking the deadlock.

Lenell John-Lewis, who had scored seven times in his last six games, burst forward and hammered a shot against Ryan Clarke's left-hand post.

The U's keeper was well beaten and it was a lucky escape for the visitors, the ball thudding back into play.

The hosts enjoyed a five-minute spell of the ball, which got the crowd in full voice.

But it was then United's turn to be on top.

Alfie Potter was lively on the right and he went close when a Jack Macreth backpass fell short, before Rose and Holmes-Dennis tried their luck from distance.

However, it was Howard who came closest with a free-kick from the right flank, that he curled in left-footed.

The ball caught the wind and looked to be heading for the net, only for James McKeown to dive back and tip it over his bar.

But United's pressure was soon to tell.

A long ball clear from Holmes-Dennis on 35 minutes saw Roberts show great pace to get their first and hold it up well on the left flank.

He then turned his man, cut inside and hit a sweet right-foot effort into the corner of the net from 18 yards.

Every U's player went to congratulate the teenager who was understandably delighted.

Howard saw a goalbound shot saved on the line by McKeown as United enjoyed a great spell of pressure.

And soon it was to get even better.

Potter did well to break clear and play in O'Dowda on the left.

Howard and Roberts were offside, but O'Dowda was not, the linesman correctly letting play go on.

The left winger burst through and his shot was saved, but Roberts was on hand to tap home the rebound from an acute angle.

It sent the travelling fans into raptures, as they chanted Roberts's name until the break.

Grimsby were sent out early for the second half, and started well, John-Lewis shooting wide.

But United soon got on top and were soon 3-0 ahead on 50 minutes.

Andy Whing won a crunching tackle in midfield, fed Potter, who in turn passed to Riley.

His cross found it's way to an unmarked Rose 12 yards out, and he lashed in a right-foot effort in front of the U's fans.

John-Lewis was going to be the home side's chief threat, and when he went down in the United box and referee Chris Kavanagh blew, United supporters feared the worst.

But the striker was booked for diving, to the annoyance of home fans.

Howard saw a shot saved as United tried to stay on the front foot.

Jon-Paul Pittman went down in the box under a Johnny Mullins challenge on 67 minutes, but again Mr Kavanagh waved penalty appeals and awarded a corner.

The hosts gave themselves a lifeline when Pearson flicked a cross home from the right.

Roberts was replaced by Barnett with four minutes to go, receiving a huge ovation from the 193 travelling support.

United comfortably saw the game out, with Roberts the shining light.

Grimsby Tn: McKeown, Parslow, Pearson, Nsiala, Thomas, Mackreth, Clay, Disley (McLaughlin 59), Arnold (Neilson 63), Pittman, John-Lewis (Hannah 70). Subs not used: Bignot, Doig, Humble, Walker.

Oxford Utd: Clarke, Riley (Meades 75), Mullins, Wright, Holmes-Dennis, Potter, Whing, Rose, O'Dowda (Brown 86), Howard, Roberts (Barnett 86). Subs not used: Crocombe, S Long, Ruffels, Collins.

Referee: C Kavanagh.

Attendance: 3,241 (193 from Oxford).