KEMAR Roofe scored twice as Oxford United chalked up their biggest away win of the season to increase rock bottom Tranmere Rovers' relegation fears.

There was little to choose between the sides until the visitors surged clear with two goals in 95 seconds early in the second half.

Roofe leapt to head in Sam Long's wicked cross to open the scoring and within a flash Danny Hylton unselfishly set up Danny Rose to double the lead.

United's No 10 also set up their third goal, midway through the half, teeing up Roofe, who did not catch his shot sweetly but it still nestled in the top corner.

The handsome victory extended the side's unbeaten run to six games and sealed their biggest away win since the 4-1 success at Fratton Park in August 2013.

It also increased the likelihood United will not be returning to Prenton Park next season, with Tranmere running out of time to avoid slipping into non-league for the first time since 1921.

The visitors' line-up showed three changes from the side which started Tuesday night's 1-1 draw at home to Northampton Town.

Chey Dunkley came in for his first action in three months, replacing Johnny Mullins at centre half.

Rose was preferred to Callum O'Dowda, while Kyle Vassell made way for Alex MacDonald, meaning Roofe was pushed up front.

A fast and furious start meant the game took a while to settle down.

The first opening fell to Tranmere on the quarter of an hour mark, when a quickly-taken throw-in caught United's defence napping.

Jennison Myrie-Williams raced clear for a golden chance, only to drag his shot wide, Aside from a corner headed wide by Dunkley, United took almost half an hour to carve out a presentable chance of their own.

Again it came from a corner. The set piece fell for Sam Long, whose close-range shot was deflected over by Rob Taylor.

Tranmere had looked fairly solid, but the anxiety around Prenton Park was palpable whenever United attacked with purpose.

Roofe came close to a brilliant solo goal on 36 minutes when a dribble, which began in his own penalty area, ended with a low 20-yard shot which flew inches wide.

It would have been a breathtaking goal, but in shooting he ignored Rose, who was in space and screaming for a pass to his right.

The midfielder did not have long to wait for a shooting opportunity, though.

Intricate one-touch passing on the edge of the Tranmere area eventually fell to Rose, whose low shot tested goalkeeper Owain Fon Williams for the first time.

It was part of a bright spell late in the half for United, where Hylton headed against a defender at the back post from a Rose free-kick.

Tranmere had the final word in the half, when a combination of goalkeeper Jamie Ashdown and Michael Collins on the goal line blocked an effort from Janoi Donacien in stoppage time.

Ashdown was also pressed into action shortly after the restart, keeping out a firm shot from Myrie-Williams.

But in a flash, the visitors took the game away from Tranmere.

Sam Long, Michael Collins and Rose teased the hosts with patient build-up, before Long crossed superbly for Roofe to plant a header past Fon Williams.

Less than two minutes later, it was 2-0.

MacDonald came in off the left flank and played in Hylton, who cleverly drew Fon Williams before squaring to Rose, who could not miss from six yards.

It looked so easy and the home fans quickly showed their displeasure.

Much of their ire was aimed at Donacien, who was quickly hooked off in a double change.

Within seconds one of their substitutes, Jason Koumas, swung in a free-kick which Odejayi headed a fraction wide.

Dunkley also needed to make an excellent saving tackle on Myrie-Williams to deny a one-in-one as Tranmere briefly threatened.

But they were taking huge risks at the back and midway through the half the game was effectively ended as a contest.

Roofe again found the net, this time with a mis-hit shot after Hylton had knocked down Jake Wright's long free-kick.

It was the cue for dozens of Tranmere fans to head for the exits.

The home side kept plugging away, but they never looked like getting back in the game.

United might have added to their advantage late on.

Substitute James Roberts had a couple of chances, hitting the post with one shot.

The visitors also handed a senior debut to Aidan Hawtin in the closing moments as they cruised to a big win.

Tranmere: Fon Williams, Holmes, Ihiekwe, Donacien (Laird 61), Taylor (Hill 72), Myrie-Williams, Power, Jennings, Green (Koumas 61), Hume, Odejayi.

Subs not used: Brezovan, Dugdale, Donnelly, Stockton.

Oxford Utd: Ashdown, Long, Dunkley, Wright, Skarz, MacDonald (Hawtin 89), Collins, Ruffels, Rose, Roofe (Hoban 75), Hylton (Roberts 80).

Subs not used: Clarke, Mullins, Whing, O'Dowda.

Referee: Andrew Madley (West Yorkshire).