Doncaster made a dream return to the Nationwide League as two-goal veteran striker Leo Fortune-West helped them to a famous victory.
The last time Doncaster visited Orient six seasons ago they were crushed 8-0 and were subsequently relegated.
But they returned in style and opened their division three points account with this victory.
The game turned on the stroke of half time when Gregg Blundell put the visitors ahead - until then Orient had dominated the proceedings in the searing heat.
But after Blundell’s strike, Orient fell away and Rovers wrapped things up with two goals from the ever dangerous Fortune-West in the half to mark an exciting debut.
Orient responded with a late penalty from Matthew Lockwood 13 minutes from time - but it was too little too late.
After the game Orient manager Paul Brush said: “The first 30 minutes was just what I wanted. But the last hour was simply not good enough.
“We didn’t take our chances or defend well enough. It was too similar to last season and I don’t want that and the players know it.†Orient had started well as Chris Tate, Gary Alexander and Tom Newey all went close - with Rovers keeper Andy Warrington tipping away Newey’s close-range header in breathtaking style.
As Orient continued to press Newey went close on two further occasions as did Alexander and Tate who hit the woodwork.
However, Orient were punished as half time approached when Blundell sent a diving header past Lee Harrison following Paul Green’s cross from the left.
Fortune-West gave Rovers a two-goal cushion in the 54th minute heading home from six yards after Blundell knocked Green's cross into the danger area.
Then Rovers wrapped things up when Fortune-West netted again from close range after good work from Michael McIndoe.
Orient responded and when Chris Beech felled Wayne Purser, Lockwood crashed the spot-kick past Warrington's right hand and into the corner of the net.