Los Blancos thoroughly dominated the first half but had to settle for a 1-0 lead at the break thanks to Ronaldo’s opener, with Gareth Bale providing the assist.
The Portugal international doubled their advantage from the penalty spot early in the second half after Roberto Lago was penalised for a handball.
Ramos made sure of the result just after the hour mark with an acrobatic effort, giving visiting keeper Boy Waterman no chance.
Northampton striker Kevin van Veen is hoping to make his first start in over a month in the home game against Shrewsbury.
Derby's decision to postpone Sunday's home Sky Bet Championship game against Cardiff was made independently, Derbyshire Police have confirmed.
Rochdale have no new injury worries ahead of Tuesday's Sky Bet League One relegation battle with fellow strugglers Fleetwood.