Thomas Mikkelsen opened the scoring with his first goal for the Dingwall club and the Dane added his second after the break.
County were firmly in control by then, with Craig Curran having struck twice in the first-half, either side of a Sean Dillon own goal.
Alex Schalk rounded off the scoring two minutes after replacing Curran.
The victory saw County maintain their 100% record in the competition and overtake fellow Premiership side Hibernian in Group D, having played one game more.
In Group D's other fixture, an 89th-minute Frank McKeown equaliser earned Alloa a 1-1 draw with fellow League One side Arbroath, who had opened the scoring in the 16th minute through Blair Yule.
Arbroath secured the bonus point, winning the penalty shootout 6-5 after Thomas Grant and Kris Renton missed spot kicks for the home side.
In Group C, a late Jack Hendry goal secured victory for Premiership side Dundee over Raith Rovers of the Championship.
The game at Stark's Park was goalless until a frantic final seven minutes, with Sofien Moussa scoring a debut goal for Dundee only for Lewis Vaughan to equalise for the home side in the 90th minute.
Hendry's winning goal in time added on moved Dundee level with Cowdenbeath and Dundee United on three points, with all three sides having played one game so far.
Ross County climbed to the top of Scottish League Cup Group D with a comprehensive victory over Montrose.