The U’s made two changes to their starting eleven for the visit to the Keepmoat Stadium, with Luke Prosser and Kane Vincent-Young replacing the injured Lewis Kinsella (ankle) and Tarique Fosu (hamstring).
It extends the U's winless run, but they'll be left wondering how they didn't take home at least a point on Saturday.
But the crucial intervention in the game came from Tommy Rowe, who broke the deadlock just before the break to earn Rovers all three points.
Doncaster are now ten unbeaten at home but the U's carved out the better chances through the game as Szmodics, Guthrie, Porter and Johnstone all came close to scoring.
Colchester United fell to defeat by a single goal on Saturday, but could feel hugely unfortunate not to have got anything out of the game at the Keepmoat Stadium.
The U’s had Vincent-Young and Wright pushed right up against their full backs in the early stages and one darting Wright run was ended as he ventured into the box.
At the other end, the home side were sharp and purposeful in the final third and it was clear that the U’s would have to be on their toes at the back.
The first sight of goal came from Guthrie for the U’s, as he spun his man expertly on ten minutes, before lifting his effort well over the bar from 25 yards out.
And they went close again nine minutes later as, from a free kick on the right, both Szmodics and Wright had low shots well blocked by some brave Rovers defending.
The U’s were getting the better sights of goal in the first quarter of the game and Porter knocked it down into the path of Guthrie on 23 minutes, who struck it cleanly and forced a fine save out of Marosi.
Szmodics then had a pair of chances. First he burrowed his way through the defence to have an effort deflected over the bar, before then almost getting on the end of Guthrie’s header back across goal from a deep cross.
The U’s had had the better of the first half an hour, but found themselves behind seconds before the break.
It was made by Marquis’ clever dummy and Rowe dinked the ball over the previously untested Walker to give the home side the lead.
It was harsh on a Colchester side who had had the better of the first period, and they knew they would have to come out quickly after the break to get level in the match.
It was Rovers who went closest first though, with Marquis’ looping header at the far post dropping just past the opposite upright.
Slater was in the wars after the break, twice grounded in heavy collisions, but manfully fought on as he protected the back four.
The U’s were next to go close, Wynter sending in a cross from the left that Guthrie flicked towards goal, going just past the far upright.
The pair combined well again as Guthrie this time headed low to the bottom corner, with Marosi saving well.
The U’s had started the half brightly, but were indebted to Eastman on 62 minutes, getting in a strong tackle, just as it looked like Rovers were about to get into a dangerous position.
Brindley fizzed a shot just wide after the introduction of Johnstone up front in place of Porter as the U’s sought the equaliser.
The U’s then introduced Macauley Bonne for the final quarter of the game as they looked to unlock the Doncaster door.
With the U’s pressing, Marquis got in clear on goal at the other end with no visiting player near him, but over egged his efforts to round Walker, allowing Brindley to get in and clear from inside the post.
The U’s were still in the game though, and Bonne slid in Szmodics, who was denied by the outrushing Marosi who fended it away.
Marquis drifted one shot wide before Walker collected another at his near post, as the margin remained at one goal into the final ten minutes.
The U’s went close again with five minutes to go, as Johnstone flashed a header agonisingly wide of goal from Sembie-Ferris’ clipped cross.
And they had a shout for a penalty in injury time as Szmodics went to ground but, after the appeals were waved away, the front man picked himself up to lift one over the bar.
It summed up a frustrating afternoon for the U's, whose endeavours deserved better than defeat.