Is it true that a Roman Catholic must attend confession if he or she miss a mass? And then would they simply be confessing just that....or do they ask for other offences to be taken into account?
As I remember it, attending Mass isn't the problem, it's whether or not you take Communion in a state of sin that's the issue. As for Confession, what happens in the Confessional is between you, your confessor and God. Ideally to take Communion one should be clear of conscience and without sin. There is another point about taking Communion and Confession but I can't remember it clearly, so I shall have to consult someone more devout then myself on that point.
You don't have to go to confession straight away after every "sin". At the end of the day swearing, missing mass, speaking ill of someone, any form of misbehaviour is a "sin" so you'd never be out of the place if you went to confession every time. I am a lapsed catholic and when I used to I'd spout off an accumulation of "sins" and then you were relieved of your sins after your penance (prayers). You can confess anything at all, from lying to sleeping with your neighbours wife to murdering someone and it's only between you the priest and God.
Sorry, I completely mis-read your question as you can probably tell from my answer. Sometimes people have to miss Mass, life doesn't take a break just because it's Sunday. I'm sure years ago and even nowadays you would get elderly Catholics and perhaps the more devout of my parents generation who would regard it as a confessionable sin. If everyone decided to confess everytime they missed Mass, the priest would never get the opportunity to say Mass. And if all the lapsed Catholics had a sudden change of heart .........