Oxford United took a major step towards League One survival as they edged out Doncaster Rovers 1-0.Substitute James Henry's second-half header was enough to separate the sides in a tight affair and move Karl Robinson's side six points clear of the bottom four.It was hosts Doncaster who were the more threatening but they could not make their pressure count.Alfie May almost produced a brilliant individual effort as he flicked the ball over Rob Dickie - only to be denied by the legs of Simon Eastwood.The Oxford goalkeeper kept out a drive by John Marquis, while Todd Kane headed over his own bar with May lurking.Matty Blair fired straight at Eastwood with a glorious chance from Rodney Kongolo's cross as Doncaster continued to push after the break.Marquis turned in Ben Whiteman's low ball but the offside flag was up.Oxford went in front on 63 minutes when Henry met Ryan Ledson's superb cross with a fine diving header.The visitors maintained their lead thanks to a fine save from Eastwood, who tipped over Marquis' sweeping shot following a fine counter attack.