Coleman said: "It was a fantastic piece of awareness from Bell and the strike was perfect. As soon as it left his foot, it was a goal.
"I don't think there are too many players on the pitch that could have done that.
"We have 50 points now and we have two games in hand on some of the teams above us. We have to keep grinding out results if we have to because it is all about how high we can finish."
The Sky Blues could have doubled their lead on 28 minutes when Stephen Wright's spectacular 25-yard volley smashed against Sullivan's left-hand post.
Doncaster threatened to equalise on 34 minutes when Richie Wellens played John Spicer in on goal but Keiren Westwood did well to parry the shot.
Doncaster started the second half brightly when Paul Heffernan adjusted quickly to flick Gareth Roberts' cross at goal on 49 minutes, but Westwood made a comfortable stop.
Dean Shiels escaped Scott Dann before finding himself one on one with Westwood, who did well to close him down at the near post and block the shot.
City responded to the pressure with an effort of their own in the 64th minute as Beuzelin's whipped cross from the left was headed over the bar by Dann.
Coventry saw out three minutes of added time to end a run of four straight defeats and move above their opponents in the Championship table.
Doncaster manager Sean O'Driscoll was unhappy with the manner in which his team conceded the goal.
He said: "It is difficult to win in this division, especially when you concede poor goals, and that was a poor goal from our point of view. It was a great finish but a poor goal for us.
"Sullivan's experience speaks for itself, he's 39 years old and I'm not going to teach him to suck eggs.
"He's tried to clear the ball further up the pitch because of Gunnarsson's long throw but in hindsight he should probably have stuck it into row Z and defended the next attack.
"We are fine at passing the ball and maintaining possession but we need to improve on some of the other things that 90% of the teams in this division can do in their sleep."