The Magpies face Latvian side Ventspils in the second qualifying round, first leg of the Uefa Cup on Thursday.
However, they are haunted by the errors led to their exit from last season's Intertoto Cup semi-final and have been sloppy in pre-season friendlies.
"Mistakes that were made can be ironed out but players of this quality should not be making them," said Roeder.
Newcastle failed to qualify for the Uefa Cup last season from the backdoor route of the Intertoto Cup when they crashed out to Deportivo La Coruna in an error-strewn semi-final.
Roeder's team have conceded six goals in two recent pre-season friendlies.
The Magpies boss added: "Maybe with them being friendlies we were a little too relaxed when defending.
"We left keeper Shay Given exposed but we have got those games out of the way now and hopefully those mistakes will be eradicated."
Kick off: 18:50 - channel 5