Roche, who faces a late fitness test on an adductor problem to end a two-game absence, feels a slack approach at the back lies at the heart of the Shrimps' indifferent start to the League Two season.
Back-to-back league clean sheets against Chesterfield and Burton were followed by a 4-2 midweek defeat to Preston in the Johnstone's Paint Trophy, with all of the Lilywhites goals coming in the second half.
"We've conceded more goals than we would have liked, that's for sure," Roche told Press Association Sport. "This time last season we were absolutely flying and were conceding very few goals.
"That's something we've got to stop and hopefully we have stopped the rot.
"We're all very disappointed to be at the wrong end of the table, but it's early days and if we can get on the good run we know we're capable of there's no reason why we can't push up the table."